Husbands best friend was murdered and I don’t know how to help

Chas

I’m kind of at a loss. My husbands best friend, who was like his brother, was murdered on 03 July in his apartment. He was supposed to be his best man for his wedding in May, but COVID ruined that. His best friend just for married and just found out his wife is pregnant with their first baby, so needless to say, it’s tragic. On top of that, they don’t know who killed him, or why. But I am struggling with trying to help him cope. He doesn’t want to talk about it AT all and seems to be going through highs and lows within a matter of 30 minutes. He has been going off on me (nothing abusive, but also out of the norm) for no reason, but I know it’s because of what happened. I don’t feel like he is dealing with it in a healthy way though. Does anyone have recommended for how to help him or has anyone gone through something similar?