Its a horrible thing- Deal with this at work and a good mate did the same last year.
Can only imagine how bad things seem in their heads that that that’s the only solution they can see.
But you’ll never fully understand it, you just have to try not to feel guilty about it, remember the good times and try to move on.
It ain’t easy and its ok to be angry at him. Speak to someone about it, rant or blab about it on here. It’ll help a bit, maybe.
Horrible situation for you but you did your best and that’s all anyone can do.
Rip.