My friends drinking problem?

My friend is 15 and he has started to hang out with 16 and 17 year olds that drink and smoke. me and my group of friends have asked him to stop before he gets caught but he says he wants to have fun and live his life. He got so angry at me that he became violent and tried to punch me in the face. Luckily i dodged it in time and my other friends restrained him. I don't know what to do! He is falling into the wrong crowd and i think he will get caught soon. On one side i want him to get caught to teach him a lesson and show him he's not invincible, but on the other side, I want to be there for him. I don't know what to do. Please help me and show me what to do!