The death of three-year-old Elijah Marsh after wandering from a Toronto family member's apartment into the bitter cold has put the focus on child safety, with one expert urging parents to stay one step ahead of their kids.

Security camera footage showed Elijah pushing his way through the front doors of the low-rise building in the city's north end shortly after 4 a.m. ET, wearing only a shirt, diaper and winter boots. He was found several hours later, huddled in a snowbank, without vital signs, and later died in hospital. 

“As parents, it’s always hard to envision losing your child. It’s probably the worst tragedy that can happen, especially when the child is so young, so innocent,” said Yehudah Franken, a certified professional childproofer based in Toronto.

“There aren’t really words to describe it.”

While the circumstances of how Elijah made his way out of the apartment building and into the cold remain unknown, police have said repeatedly it's not a criminal investigation.

Franken told CBC’s Metro Morning that kids can be clever and inventive, something difficult for parents to foresee.

“Its hard to mentally anticipate some of the milestones that kids can get to. Children are all different — some kids are very, very adventurous and some kids aren’t,” he told host Matt Galloway.

“There’s a certain amount of unpredictability as to when they can do things, but they will get there eventually.… And that’s the difficult part — to orient yourself and ask, ‘What can they possibly do?’ and then take steps to prevent it.”

Elijah missing 3-year-old boy

Elijah Marsh, 3, wandered on his own from a family member's apartment in the middle of the night, prompting a childproofing expert to urge parents to stay a step ahead of young children because of their 'unpredictability.' (Toronto Police Services)

As an expert on child-proofing homes, Franken urges putting a chain out of reach of kids on each door,which should also be secured with a flip lock.

Many parents try to stay one step ahead of curious children, which is why Elijah’s story has resonated so deeply with Canadians, said Toronto parent Justin Kozuch, who launched a crowdfunding campaign with proceeds going to Elijah's funeral.

“My son has recently learned how to drag the stool over the door to our apartment and open up the door, which was a bit of an alarming discovery that we recently made. Watching the security camera footage that was shown yesterday really hit home for me,” he said.

Kozuch's online campaign aims to raise $20,000. As of Friday morning, about 12 hours after its launch, more than $23,000 has been raised.