[narrator] A quiet relationship
with your neighbors can be a gift...
Hey, guys.
You really should open your own flower shop.
They were lovely.
It was very cordial.
[narrator] ...but following calm can come a storm.
Mark had a complete obsession with us.
[screams]
He was very creepy,
very weird, very odd.
[crying]
[Cathy] It was sheer terror.
[Paul] Mark!
All hell broke loose that night.
I was going to rip them apart.
[woman] Good to see you.
[woman shouting indistinctly]
[man] I know what you did.
[woman] Stay out of my neighborhood!
[man] Stay away from my wife!
On the ground, now!
[woman screaming]
[narrator] Located in Hamilton, Ontario,
the neighborhood of West Mountain is a haven
for many hardworking families.
[Ash Kelly] West Mountain in Hamilton
is mostly single family residence homes,
big yards, big houses.
[Dave Oleniuk] The odd little cluster of town homes
close to the escarpment in Hamilton
which is quite a nice area.
[narrator] West Mountain is where Cathy Sienna
and her daughter call home.
My parents said they were getting a divorce.
My mom found a house on the West Mountain,
so I moved in with her.
I moved into my home on Magnolia
and it was a duplex
with open concept.
-Garden's looking great, Mom. -Thanks.
The secret is the TLC it gets from my beautiful assistant.
[both laugh]
[Cathy] You know our house was the social center,
always something on the go.
It was very, very busy.
Very social.
[narrator] Also living with them is Cathy's son Mitchell.
How long you gonna tinker with that thing for?
Call a mechanic already.
[both laugh]
[Mitchell] Where's the fun in that?
[narrator] Cathy works as an office manager
and is a recent paralegal graduate.
Alex is a paralegal at a traffic defense firm.
[Alex] Mitchell worked at a car body shop,
so he was always working on a car.
Just don't work on it all night and be late for dinner.
-I'm gonna go inside and wash up. -Okay.
[narrator] Living next door to the Sienna family are the Ducketts...
Hi, Cathy.
[narrator] ...Annette and Paul...
Hey, guys.
[narrator] ...and their adopted son, Mark.
They were lovely.
They were older than myself.
Wow, look at this.
You really should open your own flower shop.
[Cathy] So it was very cordial.
No issues.
"Hi. Bye. How was your day? Your flowers look nice."
[narrator] Annette and Paul Duckett are retired.
Twenty-six-year-old Mark works off and on as an HVAC technician.
[Ash] When he was born Mark Duckett was immediately
remanded into child protective services.
He spent two years in care before he was adopted
by Annette and Paul Duckett.
Nice wheels, Mitchell.
Thanks, man. How you been?
Doing okay, uh...
You got a smoke?
[Cathy] Mark next door would come over, you know,
"Hey, bud, do you have smoke? Do you have a smoke?"
And of course Mitchell would give it to him, give it to him.
We both should quit.
Yeah, but... not today, right?
Hey, Mark, can you give me a hand in the kitchen?
Thanks.
Thanks again.
[Alex] Definitely not a friendship,
but definitely, like, a cordial, neighborly,
you know, interactions.
[narrator] For now tranquility rules in West Mountain.
-Can I come in? -No.
[narrator] But things will soon deteriorate.
Bothering my family now?
He was always very strange.
Just a strange person.
Can you give us a break, man?
Mitchell would work late and then he would be tinkering
on whatever car he had at that time.
Hey, Mitchell. [chuckles]
Got any smokes?
Mark would just appear like out of nowhere.
Look, man, I am not your endless source of free cigarettes.
Of course not.
My brother Mitchell was just trying to be nice.
One time I was home
and I heard a knock at the door. I answered the door.
I was the only one in there at that time.
Hey, is... is Mitchell home?
Are you a friend of his?
I just... I just wanted to bum a smoke.
I did not know his name was Mark Duckett.
I just knew he was the neighbor,
and he asked if my brother was home.
He's not home right now.
Okay.
Bye.
I definitely had my guard up.
The alarm bells, they were dinging for sure.
[Ash] You know, maybe Mark was reaching out
and trying to be friends.
Maybe this was his way of connecting with people.
Certainly smoking is a social activity.
I mean it doesn't seem completely abnormal,
but what it demonstrates
is a lack of sort of boundaries.
Hey, Mitchell.
I was just knocking on your door.
Got a... got any smokes?
Okay, Mark, this gotta stop. Right now.
What's gotta stop?
Mitchell's kinda shutting that down
because, you know, like, you know
one here or there is okay,
but not the knocking on the door
and asking for cigarettes, specifically.
Bothering my family now?
We're done. Right.
I don't have smokes for you, okay.
He kinda felt like that was crossing the line.
[Ash] It probably wasn't a big deal for Mitch
to just stop interacting with Mark.
What Mark felt on the other side of that,
it could have been a massive blow,
you know, to his self-esteem, to his sense of self.
[narrator] Eventually, Mitchell moves out of his mom's house.
[Cathy] Mitchell moved in with his girlfriend.
Drive careful. Please call me when you get there.
Okay, okay.
-I'll miss you. -I'll miss you, too.
So he was starting a new life.
[Ash] I think this relationship between Mark and Mitchell,
I believe the Sienna family
perceived it as very one-sided,
so despite Mark's willingness
to open up and connect with Mitchell,
it doesn't feel like
that was necessarily reciprocated.
[narrator] With Mitchell now out of the picture,
Mark becomes reclusive.
[Alex] For an extended period of time
I didn't even know if he lived there any more
because I didn't see him for a long time,
but when I did see him,
he was strange, kept to himself,
quiet, almost like withdrawn.
[narrator] The Sienna household gains new additions
when Cathy's elder son Nikko
and his girlfriend Jennifer move in.
-Hi. -Hi.
[Cathy] Well, they were renting an apartment,
it was expensive,
and it was hard for kids to get ahead,
and I just wanted them
to be able to save for their future.
He was a manager for CARSTAR, Canada.
He would oversee the operations
of 25 different collision centers.
What the heck did you pack in here, like 20 bowling balls?
Right around the time Nikko and Jen moved in,
um, Mark's behavior became increasingly weirder and weirder.
Looks like we've got some new neighbors.
[narrator] Nikko and Jen's arrival next door
triggers something in Mark's perception of reality.
[Jennifer] Can you believe we live next door to a loser like Mark?
Yeah, he should be stuck in a zoo.
-What a freak! -Loser.
[Jennifer] Pathetic.
[Nikko] Freak!
[mocking laughter]
-Oh, man! We should go bowling next weekend though. -Okay. Yeah, yeah.
[narrator] It's only a matter of time
before things turn dark and dangerous.
-Oh, hi. -I wanna talk to you about Mark.
What about him?
He went from zero to 100 in minutes.
This guy is weird. This guy's creepy.
I feel really uneasy around him.
[Ash] We know that Mark's behavior
seems to worsen after Nikko moves in,
but we don't know why.
Is this still a fallout from Mitch's departure?
[Nikko] Hey, can you, and you hold the bag straight please?
-Thank you. -[grunts]
[Nikko] You need help or?
That's okay, you need me to do that too or...
-[Jennifer] Oh... -Yeah.
...feeling a little sarcastic this morning.
[Nikko] We're watching you, Mark.
We're gonna get you.
It seems that Mark had developed a belief
that he was being watched by his neighbors.
You can't hide from us, dummy.
[Ash] The goings on
in the yard at the Sienna home,
Mark was interpreting that as a threat
to his safety, privacy and security.
Here, why don't I finish this? You go inside.
-Are you sure? -Yeah, yeah.
Just go and check on your mom, okay?
Okay.
[Ash] He's experiencing the world
as someone in an early state of psychosis
that's being projected upon the Sienna family.
[narrator] Nikko Sienna decides to raise the issue
of Mark's odd demeanor with his mother, Cathy.
-Hey, Mom. -Hey.
What's up with that guy next door?
I don't know. He just seems a little off.
Nikko was really concerned with his behavior.
Yeah, Mark, he's definitely an odd duck.
So I thought, he's just anti-social,
or he's awkward or there's something wrong with him.
I didn't really know.
Yeah, that's... that's for sure.
Hey, how about you put the pot on?
Help me cook dinner, okay?
Okay, Mom.
[narrator] Cathy likewise becomes aware of the abnormal conduct
Mark directs at the Sienna house.
[Cathy] I was waiting to get picked up
by Hauser, my boyfriend at the time.
Mark is walking between the houses
and all of a sudden he did just like, summersault midair.
And then he would sit in the chair
and then just cross his arms... and stare.
I felt really uneasy.
I wasn't sure what to make of him.
[Ash] Mark was hearing voices telling him to do things
and he thought maybe it was the Sienna family
directing him to do these things,
like acrobatic summersaults
or little flips.
-You look nice. -Thank you.
Hauser picked me up.
Mark just stared at us,
you know, with his arms crossed...
Is everything all right?
Yeah, yeah, let's just go.
...and watched us drive away
in a creepy way.
Mark, what are you doing there?
Just taking it easy.
I'll be in soon.
[narrator] Mark believes the people next door
are constantly watching him.
Mark had expressed a lot of paranoia about
the neighbors being after him.
[narrator] And the Sienna family
finds his antics increasingly unsettling.
[Alex] We were starting to feel super-uneasy
and pretty unsafe
just with the actions that Mark was doing.
We would, you know, leave and go for groceries,
Mark would be sitting
and he would just be staring at us.
Nice day, huh?
Just staring. Just didn't wave. Didn't say hello,
or anything like that.
Mark would just stare.
Just ignore him.
You have the grocery list?
[Alex] We'd come back and Mark would be
in the exact same position that he was.
It's almost like he was a statue.
He did not move. He would be just staring.
Who cares. Okay? Let's just go in.
[Ash] It's clear that Mark was experiencing
hallucinations, nonsensical illogical threats
that don't exist.
You're such a loser. [laughing]
What's wrong with this guy?
[both laugh]
Oh.
You're such a freak!
It would appear that Mark felt a little threatened by Nikko.
[narrator] These new perceived dangers
weigh heavily on Mark's mind.
He sets out to document
the harassment from next door.
[Ash] Mark purchased a camera
and put it in the window that faces the Sienna home.
[narrator] The Siennas are unaware they are being recorded.
Mark's camera would have faced
my side of the house, so my bedroom.
I never saw a camera.
I did not even know there was a camera there.
[Oleniuk] I don't know what he was trying to prove.
There is no evidence that the Siennas
had any intention to harm him whatsoever.
Lousy bastard.
You better watch your back, Mark. [laughs]
[narrator] It's a quiet afternoon at the Duckett residence,
but Mark's mental deterioration is getting worse.
[Mark crying, screaming]
-Oh, my God! -Mark!
-[Mark crying] -[Paul] Mark!
He would just scream alone in his bedroom,
and they could hear it throughout the household.
-Mark! -Mark!
-[Mark crying] -Mark, I need you to unlock this door.
Mark? Mark! Mark!
[Alex] I'm more on edge when I'm seeing him
because this behavior is not normal.
I don't think anybody involved in this
ever thought that it would get to this point.
From the Duckett perspective,
they had repeatedly witnessed Mark
locking himself in his bedroom and screaming.
Mark!
[crying]
They... No. No.
[Annette] Sweetheart, what's wrong?
What's wrong? What's wrong?
Mark, what's wrong?
[sputtering] They're trying to get me.
Who's trying to get you?
-Freak! -[mocking laughter]
[softly] No. Oh, no, no.
He has a level of paranoia
that is disproportionate to any problem in reality.
I really think it would be a good idea
for you to, maybe talk to a doctor.
No. What are they gonna do?
[narrator] Trying to compel an adult
to get psychiatric help can be a difficult process.
Well, they might be able to figure something out that...
[Ash] It's easy to imagine he would've been overwhelmed
by the prospect of seeking help,
or perhaps he actually had no self-awareness.
Perhaps he did not know that he was spiraling.
I'm okay now.
You guys can go back to what you're doing, please.
[Ash] People develop a fear of institutionalization,
where we have seen, you know, a number of abuses
against vulnerable people occur.
So I think in general there's a lack of trust.
[narrator] With his paranoia spiking,
Mark Duckett has his own ideas
about how best to protect himself.
So, the guys are gonna be working the barbecue, is that it?
And we should bring salad and dessert?
Hey, Mom, can I grab your signature?
Oh, what's it for? Just a second, Jill.
Just something I'm working on.
[narrator] In a disturbing twist,
his mother has just unknowingly sponsored
Mark's firearm license application.
-One more. -Hmm. Hang on.
[Oleniuk] Annette claims that she remembers signing
some forms, but weren't aware what they were about.
[Ash] If you're first time applicant,
you have to go through 16 hours of gun safety and gun history training.
Fill out a few forms.
Have some sponsors or witnesses sign those.
[Oleniuk] You know, they're a typical government form,
several pages, lots of fine print.
There's a certain plausibility there, uh,
who knows if Mark told her the truth.
[Ash] Mark didn't have any previous interactions with police
so there wouldn't have been any red flags
on that firearms license
when they did go to process it.
Mark after he gets his license,
he obtains a Glock 9mm pistol.
There was, you know, either a fear there,
and a belief that he needed
a firearm to either protect himself,
or there was always intent there in some way.
[narrator] Mark's attention
now shifts back to the Siennas.
CARSTAR had sent Nikko for a weekend conference.
It was in Chicago.
You two behave while I'm gone, okay?
[chuckling] Are you kidding?
Jen and I are gonna hit the clubs.
-Yeah, ravers. -Yeah.
-[laughs] -Great.
-[Cathy laughs] -[Nikko] I don't have any money.
-[Jennifer] Love you. -[Nikko] Love you.
Everyone talks about you behind your back.
Everybody.
You're actually a joke.
Your life is a joke.
-Loser. -Freak.
Pathetic.
Oh, I hope he has a good trip.
-Yeah, I always worry about him when he's gone. -Yeah. He'll be fine. Yeah.
[narrator] With Nikko absent, Mark waits for nightfall
to confront his neighbors.
My boyfriend, Hauser, had went back home for a visit.
Alex was out for the evening,
so it was just Jen and myself at home.
[knock at door]
I opened it and he was standing there.
Yes.
Can I come in?
No, you can't.
And I put my foot on the door,
and I felt very uneasy.
Um, what do you want?
We have a lot to talk about.
He was saying, "Oh, there's just so much to talk about.
So much to discuss."
What?
And I thought to myself, "Like what?"
It's late.
Then I'll address my concerns another time.
[Ash] You know that he did have some perceptions that,
you know, the world was out to get him.
Maybe he wanted to know, "Why are you watching me?
What do you have against me?
What have I done to... to frighten or hurt you?"
[Cathy] As soon as I shut the door,
made sure everything is locked,
I just knew something is off.
I was extremely uncomfortable and I was afraid.
[narrator] Mark believes his privacy and safety are under constant threat.
[Ash] He didn't think he needed help.
He did not know that there was anything abnormal
about his personal demeanor
or the thoughts inside of his head.
[narrator] The Sienna family finds it difficult to ignore
their neighbor's increasingly bizarre behavior.
[Alex] Jen basically had the same opinion that I did
that he was very creepy,
very weird, very odd.
She was very scared, too.
So after this incident of him arriving at my door at night,
I contacted the parents and expressed my concern.
-Hi, Mr. and Mrs. Duckett. -Oh, hi.
Do you have a minute?
Yeah, sure, what's up?
Um, I wanna talk to you about Mark.
What about him?
Um... he's been...
coming over to my place, and uh...
staring at us.
He's been knocking on my door, and trying to come in.
It sounds like he's just trying to be friendly.
I... I think something else is going on with him.
Um, we actually have a lot to do right now,
so can we talk about this later?
Yeah, we'll catch you later.
[Cathy] They just avoided. Just avoided.
There was no more,
"Hi, how are you?"
There was no more contact.
I think she was in complete denial
and if you don't talk about it
then it's not happening.
Sweep it under the carpet.
[narrator] The breach between the heads of the households
doesn't put an end to Mark's alarming displays.
Oh, it was... it was ongoing for weeks.
[narrator] One afternoon Alex hears a noise
in the space between her house and the Ducketts.
Sometimes Mark would be singing to himself,
or what appeared to be singing to himself.
There were no headphones that he was wearing
or anything like that.
Mark would do summersaults and then land on his feet
and then Mark would start laughing to himself.
[Mark laughing]
I don't know why I felt the need to document
what was going on,
but I just knew that I needed to take out my phone
and take pictures and take videos.
[Ash] He was having intrusive thoughts about
how he thought he was receiving commands
to perform stunts from them.
[Alex] I took a video because it was so bizarre.
Mark just looking into the window
and giving me, dude, like this
crazy stare.
-[Alex] Is he being weird? -Yep.
Get the [bleep] back.
I'm not even [bleep] kidding. Get out.
[Alex] Oh, my God. Oh, my God. Oh, my God. Oh, my God.
[Alex whimpering]
We just started noticing this more increasingly
bizarre behavior more often than not.
[narrator] Alex grows more and more afraid
of their neighbor's eccentric conduct,
and it's nowhere near its peak.
[Alex] We were starting to feel
super uneasy and pretty unsafe.
There was also a lot of times where I would just be
looking out of my window
and he would be just staring into my window.
[screams]
[Alex] I was scared because I didn't know
why he was staring at my window.
He was staring at me.
My entire life Nikko was always in big brother mode.
He was always, always protecting me
from when I was small.
[exhales] Hey, don't worry.
He's not gonna get in here, okay?
Not on... Not on my watch.
Thanks. You're the best.
[narrator] Cathy Sienna has her own suspicions
about what's driving Mark Duckett's behavior.
[Cathy] I believed that Mark has a complete obsession with my daughter Alex,
and when Nikko started living home
he became a wedge
between Mark and his... and this obsession.
[narrator] And this obsession is reaching a boiling point.
[Ash] It's clear that things were getting worse
and tensions were increasing,
at least in Mark's head.
[Alex] Mark's behavior had been building every day
over the last two to three weeks.
July 29, 2019, it was a Tuesday.
I would say, maybe 8:30 to nine o'clock p.m.
I was just hanging out in my room
and I heard a huge bang on my window.
Nikko!
I had a connecting bathroom
and then I heard a bang on that window.
-[banging on window] -Nikko!
I called for Nikko and Jen and I said,
"Mark's outside... banging on the windows."
I've had enough of this guy bothering you.
Let's go.
Hey!
-[banging continues] -Hey, could you cut that out?
[Alex] Jen and I peek through the blinds
and all we see is a light flashing back at us.
Nikko had opened the front door
and Mark was hiding in the bushes.
[Nikko] Hey, man.
Can you cut it out?
Okay, you're scaring the women.
[Jennifer] What's going on?
I think he's still out there.
[Nikko] What's wrong with this guy?
Hey! Can you give us a break, man?
Seriously.
[narrator] Cathy and her boyfriend Hauser, are also home at the time.
He's still shining a light at us.
You know what? I've had enough of this.
Like, we shouldn't have to live like this,
I said, "We are calling the police."
[dispatcher] 911, police, fire or ambulance?
We just wanna something to be done about it
because we were just being bothered in our own home
for seemingly no reason.
The cops arrive between 9:45 p.m. and 10:00 p.m.
[Cathy] We told the police what had been going on,
with the peeping in the window,
with the lights.
This guy's been spying on my sister in her room for weeks.
Yeah, look, I even have a video of it.
[Cathy] The police talked to all five of us,
and we showed him the video... of Mark.
We gave a description,
we said it's the guy next door.
You have any weapons here?
No. Of course not.
The police asked me that night,
"Do you have any weapons in the house?"
I said, "No."
So, I am assuming they would ask
the same question to the Ducketts.
Sir, I need you to stay away from the family next door from now on.
I don't understand, I haven't done anything wrong.
[Oleniuk] Couple of uniformed officers
went over and spoke to the Ducketts as well,
and uh, Mark denied,
uh, what had happened.
[officer] Just stay on your property from now on, okay?
Harassment charges will be filed
if we get another complaint.
Yes, sir.
[narrator] The responding officers don't question Mark
about having any firearms.
If there's a concern of violence
you have to check for firearm.
If there's no overt threat of violence,
it's not necessarily something that's mandatory.
That was the one opportunity that police had, I think,
to make a preventative call
and it didn't happen.
Aren't you taking him in?
No, we gave him warning.
That's it?
He's been harassing my family.
If anything happens again just give us a call, we'll come right back.
-Okay? -Wow...
[Alex] We just wanted them to do something.
I didn't really get why nothing further was done.
Come on.
-[crying] -You stupid idiot.
We're sick of you.
I've had it.
You know you're a mistake, right.
Calling the police has major implications, especially for people
with mental unwellness.
It could end in their death.
It has many times in this country.
It was never harmless, not for Mark.
How Mark perceived the police arriving
triggered him into
such an incredible state of defensiveness and confusion
that he became incredibly harmful.
All hell broke loose that night.
[Ash] Nikko and Jen, Alex,
they're all sleeping downstairs.
Cathy is upstairs in her bedroom with her partner.
The doors are locked.
[narrator] In the dead of night
Mark approaches the Sienna residence again.
Not much goes on until about three hours after police have left,
when there's a brick thrown through the window.
I had just fallen asleep and then I heard this
massive bang,
like the loudest bang I have ever heard before,
and I was like, "What is going on?"
[clicks]
What was that?
I don't know.
[Alex] Nikko goes up the stairs,
and then Jen and I are right on his tail.
-Move. -Mark.
It's... It's okay, man.
We don't have to do this.
We can... we can be friends.
We... You know, if you... Let's calm down.
Please, please don't--
The air smelt like blood.
It smelt like gun powder and blood,
glass, and it was just chaotic.
I had never heard a gunshot before
other than on TV.
What do I do, like, where do I go?
I have nowhere to go.
Don't--
I am hearing multiple shots over and over
and now I am, like, I'm in a full panic.
Oh, my God, that was... that was gunshots.
It was sheer terror.
So we run down the stairs and we had a backdoor exit.
[Cathy] And I am whispering in the phone to 911.
[whispering] Shots fired.
Send help.
I was trying to use my little voice
and it sounded so loud in my ear,
like, I thought, "He's gonna hear. He's gonna hear."
Like, "I'm next."
[gun cocking]
[gunshot]
[crying] He was shot 12 times.
Nikko didn't have a chance.
He was shot in cold blood
and he was shot repeatedly.
[Alex] We get out. We run out the doors,
and we go up the side of the house.
You're okay, you're okay? Yeah. You're okay?
We have to cross the street.
So I said to Jen, "We are gonna run out.
We're gonna go to the neighbor's house."
And I'm in front of Jen, I kinda put my arm out
and I stop her and I peek over.
And then I see Mark Duckett run out of our front door
and I see him getting into his car
and he drives away.
-[engine starting] -[wheels screeching]
We go back into the house and there's glass everywhere.
[both gasping]
[both screaming]
And then that's when I see Nikko lying on the floor.
No! Nikko! [crying] Not my brother!
[Cathy] And then the next thing I heard was...
"Not my brother!
Mom!
Not my brother!"
And as soon as I heard Alex...
Oh, my God. Go! Go!
I opened the door.
Oh, my God! Nikko!
[crying]
And there was Nikko laying on the floor face down,
in a pile of blood.
[all crying hysterically]
My brother's been shot. What do I do?
At some point I had both Jen's phone
and it was either my phone and my mom's phone,
but I had two phones up to my ears.
Okay, everybody listen...
I had the other people saying,
"Okay, this is-- You need to do CPR."
You have to turn him around if we have to start CPR, okay?
[Cathy voice-breaking] For CPR we have to turn him over
and I turned him over and...
he was so heavy it took
me and Jen so hard to get him to turn over.
Jen was like out of her mind, distraught.
I was doing chest compressions.
[Alex] Mouth-to-mouth. Okay? Try it.
[Cathy] And then she was, like,
"You have to blow into his mouth now."
Doing it right now.
-[crying hysterically] -Nikko!
[Cathy] I was covered in blood.
And I kept trying and I tried, and I tried
and I kept trying.
And I was praying to God, "Don't take my son."
[sirens approaching]
[Cathy] And then the paramedic showed up.
And they took over.
[all crying]
[Cathy] And the ambulance never moved.
The ambulance never moved.
I knew then my Nikko is gone.
I knew he was gone.
[narrator] Nikko Sienna
is pronounced dead at the scene.
The gunshots next door
don't awaken Annette and Paul Duckett,
but their son's text do.
[Ash] He texts his mother a string of text messages
about how being adopted
has somehow led him to repeat the failures
of his biological parents
in the... in the actions he has taken.
Paul.
-Paul, wake up. -What?
-Something's wrong with Mark. -What?
[Ash] Then his mother is texting him back
at the time saying, "What have you done?"
His parents are aware something awful has happened.
But clearly not understanding exactly what has happened,
and the magnitude of... of the crime that's occurred.
[sirens wailing]
I ran over to the neighbors
and I was going to rip them apart,
because they did nothing.
This is your fault!
My son is dead!
And the cop grabbed me at the last second
and I did not care at that point...
'cause I knew my son was gone.
[narrator] With both houses as potential crime scenes,
the Sienna and the Duckett families
are each brought to the police station.
We also had the Ducketts leave their home
because we had to conduct a search warrant,
and examine their home as well.
[Alex] They drove us to the police station
and we were there for what felt like an eternity.
[Oleniuk] Mark Duckett drove to the Mountain station,
which is about 15 minutes away.
He then, uh, left the gun
on the front seat of his car,
walked in into the Mountain Station
and laid down on the ground in the front, spreadeagled
and surrendered and said, "I just shot my neighbor
and I am turning myself in."
So the fact that he acknowledged what he did
was obviously a crime
and necessitated a response of the police,
he received legal advice and adhered to that advice,
all made us believe
that he was criminally responsible for the act of first-degree murder
and that's why we arrested him.
[narrator] Mark Duckett is charged and arraigned.
[Ash] After the charges are first filed,
that Mark's defense team decided they're gonna go with
and approach a defense of not criminally responsible.
We know he was later diagnosed with paranoid schizophrenia.
[narrator] With this diagnosis, the court ultimately finds
Mark not criminally responsible.
[Alex] Do I think Mark Duckett had something wrong with him?
Sure.
Do I think that he was having a schizophrenic episode
the night that he killed my brother?
Absolutely not.
I whole-heartedly believe that he retaliated
because we called the police on him.
[Ash] Mark is currently at a psychiatric hospital.
It's about an hour and half away from Hamilton.
[narrator] Annette and Paul Duckett still live in their home.
They must now deal with the consequences
of their son's brutal violence.
Annette and Paul remain in contact
and in support of Mark
and in hopes of his rehabilitation.
Will he get out again? There is a possibility.
If Mark is ever released
he's coming after my family,
the rest of us. He's gonna finish the job.
That's my fear.
I'm very, very scared.
[narrator] Cathy Sienna has filed law suits against the city, the police,
and the Duckett family.
The justice system has just failed us on every level.
I am advocating for
stricter gun laws,
more follow up,
more background checks.
A deeper delve into the psyche of these people that are getting guns.
[narrator] The community of West Mountain
is left shattered by Nikko Sienna's murder.
[Cathy] You know some people's lives
will never be the same again.
Jen moved out of the city.
Hauser moved out of the city.
[Ash] Hundreds and hundreds of people
showing up to memorial services
that were held for Nikko.
You know, people are naming their children after him now.
They really are wanting to memorialize the joy
that Nikko brought into their lives.
[narrator] Cathy sells her home and moves away.
She and her family have lost a beloved son and brother,
but are determined to keep his memory alive.
[Alex] You know Nikko's spirit, it lives on.
It lives on with us all the time,
and I try to live life the fullest like he did.
[Cathy] He was a beautiful soul, you know?
And I have him right here.
And this is how I have to remember my son...
in these ashes.
It's devastated this whole family.
We'll never be the same.
Never be the same.
Broken heart forever.
Next time on Fear Thy Neighbor...
Donna! Anne!
Great to see you.
There's not a closed door there.
Everyone was always invited.
When Anne moved in, it was a big change.
She's crazy.
It was a nightmare.
She was out for blood.
What does she have to do kill somebody?
[gun blast]