Unfortunately, it's pretty common. A few years ago, my son was stationed at MCAS Tustin, in SoCal, and the had a pretty bad gang problem on base, and neighboring El Toro had a HORRIBLE gang problem...they ran the barracks, and the rec halls...dealt drugs in the open, etc...Both bases have been closed since then, and consolidated into MCAS Miramar, and most of the problem has been dealt with, but it still exists.
There was a case here last year, of a local gang member who enlisted in the Marines, went off to Iraq for a tour, came home on leave, and rather than return, went gonzo, shot 2 cops before he was killed himself...The local hispanic groups called him a hero who was dealing with lots of PTSD issues. Turns out, he had never seen a single day of combat, and just pussied out, rather than go back...
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2005/01/16/BAG8GARA4M1.DTL
http://www.townhall.com/opinion/columns/michellemalkin/2005/01/19/14278.html