A 14-year-old Hamilton student was fatally stabbed, while his mother was with him, outside Sir Winston Churchill Secondary School on Monday, police said.

The teen was attacked just before 1:30 p.m. ET and died shortly after in hospital. Police have three suspects in custody and are searching for two more. One of those in custody is also 14, another is 18.

"When I look at this … it's a complete disregard for human life, which is extremely concerning for people of such a young age," said Det.-Sgt. Steve Bereziuk, in a news conference Monday evening.

Bereziuk said the stabbing was captured on video, which police are reviewing. He added both of the outstanding suspects appear to be in their early teens and one of them is female.

The detective would not say why the teen's mother was near the school, in the city's east end, but said she was not hurt in the attack.

"She's witnessed something horrible here. She's distraught. She's devastated."

Hamilton police say the teen's mother was with him when he was attacked outside Sir Winston Churchill Secondary School Monday afternoon. (Dan Taekema/CBC)

Police responded around 1:23 p.m. to what was originally described as a "serious assault," and put Winston Churchill and four other area schools under lockdown. Just over two hours later, Hamilton police announced that the student had died.

The community is in shock, and "our hearts are broken," said Manny Figueiredo, director of education at the Hamilton-Wentworth District School Board (HWDSB), in a statement Monday evening.

"Our entire community shares in the grief and sadness of having lost a valued and loved student," he said. The victim's name has not yet been released.

School principal Marco Barzetti sent a letter home saying the school would have support staff on hand Tuesday to assist students. He encouraged any who were struggling with the tragedy to speak to him or their teacher. He said flags would be lowered for three days.

Residents in the area of the school witnessed parts of what transpired and the aftermath.

Alice Smith, who has lived just down the road from the school for the past 14 years, said she was sitting in her front sunroom with her husband on Monday afternoon when five teens came around the corner, with a car following close behind.

Smith said it appeared to her the woman in the car was trying to help the boy.

"She said she tried to save him, but she just couldn't do it," Smith said. "She was very upset. She couldn't stop crying."

Smith said crowds of students pass by her house each day on their way to grab lunch at nearby stores and restaurants. She said she hopes if any of them are ever afraid or in trouble, they'll knock on her door and ask for help.

Alice Smith spoke with a woman she believes tried to help the young boy who died today. Smith says the woman couldn’t stop crying. Smith says she also has a message for any kids who are afraid. “They can come to my door and I will let them in.” <a href="https://twitter.com/hashtag/HamOnt?src=hash&ref_src=twsrc%5Etfw">#HamOnt</a> <a href="https://t.co/YaP9c2UUhu">pic.twitter.com/YaP9c2UUhu</a> —@DanTaekema

"This should not be happening. Kids should feel safe to go to school," she said, her voice breaking. "Now we have a young boy that's dead and that really upset me."

Kandace Brenn, who also lives in the area, said she knew the victim and he had been a visitor to her house. She described him as a "sweet, quiet kid" who kept to himself.

She said her niece called her to give her a lift. The niece wanted Brenn to drive her and her best friend to the Hamilton General Hospital emergency room, where the victim had been taken. Both girls are students at the high school, and her niece's friend was the victim's girlfriend said Brenn.

"As soon as I got to them, I just started breaking down, 'cause I knew it was bad, the look on their faces. She couldn't even breathe."

In the car on the way to the hospital, she said the friend described finding the victim unconscious and bleeding. Later she got a call from her niece that he hadn​​​​​​'t survived.

"She doesn't know how to cope she doesn't know how to help her best friend through it," said Brenn.

Brenn said the victim had a rough start to high school, with bullying and being picked on. But she did not know if that had any connection to what happened Monday.

A backpack and two medical packs can be seen lying on the back lawn of the school, surrounded by police tape. (Dan Taekema/CBC)

Asked whether the victim had been bullied, Bereziuk declined to go into detail, saying only that he was aware of a "relationship" between the teen and those who allegedly attacked him.

The detective also said he believes some of the suspects were students at the school. Police are still working to determine what role each suspect may have played.

The Major Crimes Unit has taken over the investigation. Investigators have not recovered a weapon and are asking residents near the school to carefully search their properties for a knife.

Anyone with cellphone video of the attack is also asked to contact them.

A large area behind the school was taped off, with the bulk of that area outside of school property. The school is just north of Main Street East, near the Queenston traffic circle, in Hamilton's east end.

.<a href="https://twitter.com/HamiltonPolice?ref_src=twsrc%5Etfw">@HamiltonPolice</a> say a 14-year-old male student from <a href="https://twitter.com/Churchill_HWDSB?ref_src=twsrc%5Etfw">@Churchill_HWDSB</a> has died as a result of injuries after an assault outside the school in <a href="https://twitter.com/hashtag/HamOnt?src=hash&ref_src=twsrc%5Etfw">#HamOnt</a>. Here’s a look at the scene. <a href="https://t.co/QoCpltlf52">pic.twitter.com/QoCpltlf52</a> —@DanTaekema

When students streamed out of the school after the hold-and-secure was lifted, they found several blocks behind the building, between Adeline and Walter Avenues, taped off and a heavy police presence. Some kids asked police how they could reach their parents, with officers turning them around and telling them they'd need to find another way through.

Behind the school, where Ivon Avenue ends at Dunsmere Road, a pair of medical packs could be seen sitting on the grass with a student's backpack lying a few metres away.