It's natural to feel upset at him. That is usually one of the first reactions in a situation like this, "Why did that person do this to ME?". Soon though, you'll have to look at the bigger picture. Your friend didn't do anything to you, he did it to himself. It's quite possible that maybe feelings of letting his friends and/or family down contributed. But you have to realize that when things like this happen, there can be many untold reasons that lead to this path.

What you are feeling is normal. The best thing to do at this point is to be supportive of his family and the friends that you share. Death is not finality, it is moving to another level, to another space. Your friend is with you and probably always will be. Maybe you should 'talk' to him, tell him how you feel. Let your emotions go. Remember all the good times, don't dwell on the bad. Death is the time to remember the very best of people because everyone has something about them worth remembering and holding on to.