Sorry to hear about your friend. That's got to be tough to deal with. Prayer made! Lifemal remember this "The effective, fervent prayer of a righteous man avails much. " Jas 5:16
I'm sorry to hear that. I had a very similar incident happen to me, and can imagine what your friend is going through. Tell him to keep his head up. Only time can help you deal with something like this... tell him to stay strong, it's going to be tough for a while, but things will get better. My prayers go out to him and the family of the deceased.