Unfortunately, I've known way too many addicts in my life, and from an objective standpoint I probably am myself a functioning alcoholic... Story for another day, but my point is that this is typical behavior of somebody that is on a bender, depressed, and is withdrawing from the outside world to just self medicate. It's a dangerous situation for him personally as obviously it's possible to overdose and die, or drive under the influence and kill someone.
Hopefully he gets into the right program and gets the help that he needs before it's too late. Addiction is a truly monster of a disease, and it's really the black plague of our generation.