I just lost a friend how's son is always drunk,what should i do?

before his mom die he got strat ''a''s was the sweetest and nicest boy you could ever meet , but then his mom she was killed by a drunk driver how also died. he cryed for 2 days none stop.then one day i found him smoking in drinking in his room. what should i do? i have 2 kids of my own and i'm scaryed i might lose him and my kids to drinking and smoking.