A three-year-old Toronto boy died in hospital after spending hours outside in the bitter cold after wandering away from the apartment building where he was staying with family around 4 a.m. Thursday wearing only a T-shirt, diaper and boots.

Elijah Marsh was found without vital signs on Baycrest Avenue around 10:20 a.m. ET yesterday, just a few hundred metres from the north-end apartment where he was spending the night with family.

Just after 2 p.m., police confirmed he had died.

'Tucked away in the corner'

Elijah Marsh walked out into the frigid Toronto cold around 4:20 a.m. ET Thursday, wearing only a T-shirt, diaper and boots, according to this image, taken from a security camera in the building where the three-year-old was staying with family. (Toronto Police Services) Insp. Frank Barredo said Elijah was found "tucked away in the corner" in the backyard of a home and that two volunteer searchers were the first to come across him.

The boy's family awoke Thursday around 7:30 a.m. to find he was missing from their low-rise apartment on Neptune Drive in the Bathurst Street and Highway 401 area. They last saw him when they put him to bed around 9:30 p.m. ET Wednesday night, police said.

Barredo said security camera footage from the building showed the boy pushing his way out the front doors of the building around 4:20 a.m. It was –19 C at that time, but felt more like –28 with the wind chill.

"He left that doorway and made his way out — the exact route we can't tell you. We may be able to find that out, we may never find that out, but we know where he ended up," Barredo told reporters.

A city mourns

The spot outside a home on Baycrest Avenue where searchers apparently found Elijah on Thursday morning. (CBC) Mayor John Tory offered his support to Elijah's family while speaking to reporters this morning.

"It is a terrible tragedy," he said.

"My heartfelt condolences to the family … Toronto's thoughts and prayers are with you during this difficult time," he later tweeted.

"I think every Torontonian will feel the loss," said police Chief Bill Blair.

"I think it'll remind all of us to go home and just hug our kids a little bit more. And I think we all will grieve for that child and for their family and for their community for its loss."

Federal finance minister and Toronto MP Joe Oliver also expressed his condolences. "Our thoughts and prayers go out to the family of Elijah at this terribly difficult time," he said from Ottawa. "The loss of a child or grandchild is an unimaginable loss. We stand with the entire community in mourning today."

Social networks lit up with efforts to find the boy during the day. When it was announced he had died, the Twitter hashtag #RIPElijah emerged, with notes of sadness, shock and condolence being posted.

An online campaign to raise $20,000 for Elijah's funeral costs has already raised more than $15,000 as of early Friday morning.

Earlier Thursday morning, police set up a command post in the area and launched a massive search that included officers from every division in the city, and canine and horseback units.

Barredo said more than 100 officers were involved in the search, and that volunteers came from across the Greater Toronto Area to assist.

"Certainly the community stepped up and we are thankful for it," he said.

'Good-natured little boy'

Rachel Eizentil lives at the address where Elijah was found. The mother of three young children told CBC News she was devastated when she learned the boy had made his way into her backyard at some point. She said neither she nor her husband heard anything during the night.

She said her sister-in-law called her shortly after she woke up to let her know about the search for the missing boy in the neighbourhood, but Eizentil said she didn't think to look in her own backyard.

She recalled how she watched from a window as a man made his way into her backyard, where he eventually found Elijah huddled near a window well.

Milly Dyer, who lives in the building where Elijah was staying, described him as a "good-natured little boy" who was a "little bit shy" at times.

"He's a typical three-year-old," she said.