Lunch was over and students at Sir Winston Churchill Secondary School in Hamilton were back in class when a man, his eyes burning after being hit with bear spray, burst into the building.

Shawn Wagar ended up in the school's auto shop and was washing away the stinging spray when he found out the 14-year-old he'd been trying to help outside the school moments before had been stabbed.

Devan Bracci-Selvey was dead, fatally stabbed in the back in front of his mother on Oct. 7.

He died in her arms on the street behind the school.

Two brothers, a 14-year-old and an 18-year-old, have been charged with first-degree murder. Police allege the 14-year-old is the person who stabbed Devan.

Wagar — who lived near Devan and is the father of one of his closest friends — is still struggling to understand what happened and his role in it: How could a confrontation over a stolen bike and building frustration about bullying have ended with a high school student dead?

Photos of Devan Selvey sit among stuffed animals, flowers and messages of support at a makeshift memorial outside the 14-year-old's Hamilton home. (Dan Taekema/CBC)

He said he sometimes wishes he was the one who died.

"They should have done me, stabbed me. And left a 14-year-old to live," he said. "But unfortunately it doesn't work that way. It's a situation where I'm going to have to live with it."

Hamilton police have remained tight-lipped about their investigation, but they have said there was some sort of "precipitating event" that took place before the stabbing.

CBC News has spoken to several witnesses and some of the people involved to piece together the critical moments that led up to the stabbing, which followed weeks of parental concerns being raised with school officials and police and came just minutes after a clash involving adults and kids outside the school.

Many details about the attack remain unclear and there continue to be conflicts between the narrative from officials and what people who knew Devan say happened.

For Wagar and other families in Devan's neighbourhood, the events that led up to the stabbing are closely connected to an act of sacrifice and a stolen bike.

That's despite the fact police have repeatedly stated none of the people arrested in connection with the stabbing were involved in the bike theft, which was investigated, but no charges were laid.

Just two days after he died, Shari-Ann Selvey, Devan's mom, explained what she believes led to her son's death during a tearful interview with media.

She said Devan had been targeted by bullies since the second day of school, when he and his friends were jumped and chased by a group of kids. All of them were older, except for one.

That same night, they were jumped again, and this time the kids tried to steal their bikes.

Selvey said Devan told one of his friends to run and gave up his bike to save theirs.

"That's the heart of Devan. He saved his friend and left himself there."

She said a group of kids had harassed him ever since.

Shawn Wagar says he wishes he was stabbed instead of Devan Bracci-Selvey. 0:34

Devan and his two friends Brody Wagar and Mikey Mcentee were so inseparable their parents sometimes referred to them as the Three Stooges.

Wagar is Brody's dad. He remembers his son coming home with a black eye the night Devan lost his bike.

He said online messages and threats bounced back and forth on social media in the weeks that followed, scaring the boys and making them worried about going to school.

'We trusted the system and the system failed'

Wagar said he and his fiancėe, along with Mikey and Devan's mothers, took action, speaking to staff at Churchill time and again about the bullying he says their sons were suffering.

He spoke to staff twice himself, while the mothers went "at least once a week."

Wagar said the families were told the principal would speak with the students involved, but the harassment continued.

"I was getting tired, but what else are we supposed to do? We trusted the system and the system failed."

When asked after Devan's death whether he felt the Hamilton-Wentworth District School Board had failed the teen, director of education Manny Figueiredo told CBC News it was premature for him to say for sure, but he doesn't believe that's the case.

The mother of the Hamilton teenager who was stabbed outside his school, told reporters that Devan Bracci-Selvey was targeted by bullies and “everyone failed" him. 2:47

He declined to say more, citing the ongoing police investigation and the board's own inquiry into what happened.

Both the school board and police have confirmed they were notified of bullying incidents involving Devan.

But the sense of concern among the parents was so heightened, said Wagar, that on the day of the stabbing, they hurried to the school for a different situation that had them worried about their children's safety.

They say they met with administrators after learning that a student who was not supposed to be at the school because he was suspended was around Churchill. They intended to take their children home.

That teen is not one of the people accused of murder in connection with the stabbing.

A backpack and two medical packs can be seen on the back lawn of Sir Winston Churchill Secondary School on the day of the stabbing. (Dan Taekema/CBC)

But just as they were about to leave, Wagar said Devan pointed out a group of teens sitting on the steps of the Pat Quinn Arena across the road, saying some of them were the kids who took his bike.

Wagar headed over to confront them, with Brody and Devan walking behind him.

Wagar said his goal was to find some sort of solution — something that would stop the teasing.

"I went there to resolve a problem, to extinguish any flames and bad feelings toward one another," he said. "That was my intention. It didn't work."

Before he even reached them, Wagar said, the kids on the steps started yelling and warning him to stay back.

Wagar stands about six feet tall and said it's possible his size was intimidating and escalated the situation in some way. But, he said, he tries to stay calm and collected unless someone crosses him.

He said he took off his glasses, thinking it was possible one of the kids might try to throw a punch as things got more heated, but he wasn't expecting what happened next. And he had no idea what started on those steps would end in a stabbing.

Suddenly, Wagar said, one of the kids pulled out a can and sprayed something in his face.

"He just let that thing rip, so I lunged forward to grab him,"said Wagar, explaining that as the spray spread among the group, the scene became chaotic.

Devan's mother, Shari-Ann Selvey​, makes her way through the crowd to join family and friends at a vigil held outside the school two days after his death. (Justin Mowat/CBC)

The spray coated his face and hair, even his ears. He said it blinded him temporarily and stained his clothes.

His recollections match closely with those of Riley McCauley, who was walking to the arena to meet friends when he saw what he describes as a tense confrontation between a middle-aged man and some kids.

As he got closer, the 18-year-old said he saw the man and one of the accused teens in each other's faces, yelling.

McCauley said the older of the two accused told the man to back off or there would be trouble. Then, suddenly, the teen pulled out a can of bear spray.

"I got caught in the friendly fire," said McCauley, who said the spray got in his eyes, causing him to tear up and run into the school to find something to wash them out.

Before he went into the building, the 18-year-old said he saw a group of students, including the younger accused, heading down the road after Devan.

Riley McCauley, 18, says he saw a confrontation between a middle-aged man and some teens in front of the Pat Quinn Arena on the day of the stabbing. (Ellen Mauro/CBC)

The sight of Devan being chased down the street is the last thing Wagar saw, too. He said Selvey, who had been sitting in her car in front of the school, drove up to him to check in before heading off after her son.

His eyes stinging, Wagar ran into the school in search of relief.

Police have confirmed a can of pepper spray was found in a driveway near the school, but haven't said more about it, except that it forms part of the evidence of their case.

Wagar and McCauley can't speak directly to what happened next because they were inside the school, and Devan's family has not publicly discussed it, but there are fragments from other witnesses.

'Everyone failed my son'

Alice Smith, who lives about a block from the school, said she saw a group of five people coming around the corner with a gold-coloured vehicle close behind.

A video captured on her security camera shows a pack of kids walking down the sidewalk.

Smith said she saw the vehicle stop several times, adding the woman inside appeared to be trying to help a boy.

It wasn't until emergency crews rushed by that she headed over to the scene. When she arrived behind the school, she found a woman in tears and a teen with blood on his face being loaded into an ambulance. Later, after she saw photos of Devan and his mom, she realized what she had witnessed.

Alice Smith said she saw a woman in a car trying to help a young student who was being chased the day Devan was killed. (Dan Taekema/CBC)

Speaking with reporters about her son's death, Selvey said he had suffered through bullying and more should have been done to help him. She often felt she was the only person who had his back — and it wasn't enough.

"Everyone failed my son. Even I did. I tried to save him and I couldn't. I couldn't get to him in time."

Selvey has declined to say more about that day except that every time she shuts her eyes, she relives what happened.

"I haven't eaten. I haven't slept. Every time I close my eyes it's there, so I don't close my eyes."

Paramedics say emergency crews were called to the school around 1:20 p.m. and found Devan on the street with traumatic injuries to his back. He was taken to hospital without vital signs.

Inside the school, students were in lockdown. McCauley, his eyes still welling up from the spray, started to hear on social media that something had happened outside.

When the lockdown was lifted, he learned there had been a stabbing and Devan was dead.

'No one wants to seem like an easy target'

McCauley graduated from Churchill last year and said it's not uncommon for students there to carry a knife or bear spray for protection. He said the school can sometimes be a rough place and the neighbourhood that surrounds it can be tough, too.

"It's Churchill. You gotta expect what you gotta expect," McCauley explained. "No one wants to seem like an easy target.I think people that think they could be vulnerable ... want to have something to make them feel at ease."

Figueiredo said the school board takes student safety seriously and has "zero tolerance" for those found in possession of a weapon meant to cause or threaten harm. It's grounds for immediate expulsion, he said Wednesday.

Despite what he's seen at the school, McCauley said the fatal stabbing still shocked him.

"It's such a waste," he said, adding it's "crazy" a 14-year-old is dead and 14-year-old and 18-year-old are in jail — for what?

Wagar keeps asking himself the same question.

He's run through the rapidly escalating events of that day over and over.

Wagar's worries that he was the trigger that led to things going so wrong are compounded by concerns for his son and Mikey. The boys were out of school for several days after the stabbing, but have since headed back to class, alongside students who their parents fear know what happened and may have even been involved.

A memorial complete with candles and flowers started in front of Bracci-Selvey's home after his death. (Dan Taekema/CBC)

When asked about how it plans to manage relationships between those students and ensure their safety, the school board declined to comment, citing the ongoing police investigations and privacy concerns.

The school board has committed to conducting a formal review of its bullying prevention practices once the police investigation into Devan's death is complete.

Figueiredo said that inquiry will provide trustees with "independent feedback and recommendations on how to prevent, intervene, report and respond to bullying."

For his part, Wagar said he feels the school and police share the blame for failing Devan by not taking the bullying situation seriously enough.

"I don't think anybody was taking anything seriously," said Wagar. "The system does not work that well to address this bullying situation."

He also wonders what will become of the two teens accused of killing Devan.

"Are these children that far gone at that age that there ain't help for them?" Wagar said. "I feel sorry for the individuals that have done this. I really do."