[mymnarorump]

I think Nomadic is right, there is something that is affecting your brother emotionally & also think that is the heart of the problem.
I have a cousin who was in a similar situation at age 16, his parents where divorced and didn't try showing love, rather they tried the hard love approach.
He is now 33-34 and has been in and out of prison since the age of 16, he has 2 daughters who were both born in prison by different drug addicted incarcerated women who also live the drug addict life going in & out of prison constantly.
Someone else mentioned something about a letter left in a troubled teens room, what an excellent idea. From what I have learnt is that when a drug user wakes up he is usually coming off the effects of the drugs he has taken & this is his lowest point & the point where things like letters & love could help him out & where he would be more unlined towards violence if approached the wrong way.
I think you need to find the heart of the problem, get him to open up to you or your parents, if you are persistent with a loving approach he will eventually give in inshallah.