With the advent of pot legalization in Canada I know quite a few people who grow their own (four plants max per person). Some have made their own gummies and have told me the effect hit them suddenly like a ton of bricks, to the point they refuse to partake again or at least drastically reduced amounts. So I wouldn't be surprised if this young man took some form of edible and started feeling some powerful effects and got scared and paranoid.
I don't see a 15 year old boy drinking and getting wasted when his mom was going to pick him up and would know immediately what he'd been up to and possibly put a kibosh on his partying in the future.
Whatever happened it's a terrible tragedy for all involved, his mom especially. She'll never forgive herself for granting him that freedom. If LE has deemed the death not suspicious it seems like that's the end of it. However, I will say, as a Canadian who's heard of a litany of poor investigations led by the RCMP in recent years I hope we get an official statement of what happened.