[Trunks]

Well, first and foremost, RIP to your friend. The why is a bit harder. I suppose there are a lot of reasons. As some said, possibly a non-evident mental disorder.

It could also be, that his family/parents weren't too great to him as he was growing up, and he got freaked out when he thought to himself, what if I ever do something like that to my kids? I know some people are just overstressed, and want to just do something, anything about it. They put on a happy face for family and friends, but when they leave, the stress/worry all comes back.

And possibly, he is just afraid of, well life....With all the shit going on/happening in the world, to some people, suicide might feel like a welcome option. I'm sorry I am not of any more help, and I wish you, your family, and his family luck with coping with such a loss. I am truly sorry.