Losing a friend at such a young age and under such troubling circumstances can be one of the most difficult things a person can go through. We're very sorry for your loss :-(.
Often there isn't much that can be said to a person to "make them feel better" but I can try to explain what a person generally goes through when someone close dies.
1) Denial
2) Anger
3) Bargaining
4) Depression
5) Acceptance
People generally go through these feelings on the road to accepting the loss that they have gone through. You should try to dive deeply into each stage. Often we try to skim through one or more of the grief stages to get to that acceptance point, but if we don't really take in each emotion, we often end up moving back wards. So don't be afraid to feel this. It's part of your life, and it's something that is going to change you forever.
The important thing to do on the road to acceptance is to make sure you aren't getting caught up in guilt or caught up trying to change something that you cannot control. This person was a gift to your life. He was someone who changed you and cared about you, and ultimately you have to see his life in this way. Even though he passed away, he still was a gift to your life.
Don't expect this to go away any time soon. Your brain has to change and re-think its entire reality. The new reality your mind is trying to accept is one where this friend, this love, is no longer around. It takes time.
We're always here for you, so don't hesitate to call or write. Take your time and focus on how much you appreciated this person for their life, not how angry you are about their death.
Boys Town Counselor PW