Well, I think there's been very good reporting on this, and it's very, very clear that the Army was well aware of disciplinary problems, of violent acting out, of mental instability over a period of time. At one point, he had the bolt removed from his weapon because there was fear that he would harm himself or others. He attacked a superior officer with his fists. There was a very vigorous debate about whether he was qualified - that is, mentally stable enough - to serve overseas. And I got the impression that the Army just very much decided it needed intel analysts. And that overrode whatever concerns some within its ranks had expressed about whether he was fit to serve.
http://www.npr.org/templates/story/story.php?storyId=207458025