Coming from a mom who has 2 younger kids with mental health issues and major abandonment issues (they are both adopted)-and this may be a foolish question--but has he seen a therapist? Has he ever processed the loss of his mother. You raised him, but there still may be a big hole in his heart.
Just like many adotped kids wonder why their birth mothers left them. Or even our kids ask why their parent won't stop drinking or drugging so they can be a whole parent. I would imagine he wonders what he did to make her commit suicide (kids think that way sometimes).
My kids have been in therapy for 4 years processing this stuff. It is hard and I am not looking forward to puberty or the day when they decide to leave the house. Hopefully they will be much healthier.
Good luck. It is hard. If he has anger issues perhaps best to address them soon before he gets himself into trouble. I know he is chronologically an adult--but how old is he emotionally?