Cathy Kinsman was in her suburban home in the Fort Richmond neighbourhood of Winnipeg on Wednesday night when fellow neighbours came rushing to her door to ask for help.
"They were saying the little boy was stuck in the snow and they needed help to try and get him out," Kinsman said.
"So we all put on our coats and ran outside and (started) digging, digging, digging away. He was pretty much buried on his chest and his legs, so we all just dug with our hands and whatever to get him out."
The adults brought the unconscious boy indoors and started performing CPR until paramedics arrived several minutes later and rushed him to hospital, she said.
Police confirmed Friday the boy had become trapped in the snow. They said it was unclear whether he had been digging a tunnel or doing something else. They said he was taken to hospital in critical condition.
Such cases are uncommon but not unheard of. A snow fort or tunnel can look sturdy but can collapse and trap people underneath, said the head of a Winnipeg-based survival school.
"If you're lying flat in there, head first, and several feet of densely packed snow fall on you, it could pin you," said Dave MacDonald, a former search-and-rescue technician who runs the International Canadian School of Survival.
People can also become disoriented and have trouble breathing under heavy snow, he said.
MacDonald suggested that parents can make efforts to monitor their children while they play in the snow. Kids can also use walkie-talkies to stay in touch and should be taught to build at least two entrances to any snow tunnel, he added.
Kinsman said neighbours are rallying around the boy's family members. She did not want to identify them — neither did police —but said they were new to Canada.
"He's a lovely little boy. He loves to play outside, especially to be in the snow. I think that was new for him," said Kinsman, who didn't say where they were from.
"He was learning English, and his mom as well, and trying to learn about being in Canada. Just a nice family."