I'm sorry to say that I've been in your shoes, twice before, both times due to DUI drivers...first my best friend and then our children's wonderful baby sitter, she was a HS senior.
I am sorry for the loss of your friend, for the pain that you, his friends, and his family will feel so deeply for quite some time. For me I spent a year of two wondering why....why him....what my wife would do had it been me...why did the legal system fail to punish these DUI drivers....
again, sorry for your loss