Austin Bay is right. Nibal Malik Hasan has committed treason. There is no other charge that is possible at the moment.
Hasan's treachery is more like that of America's most infamous traitor, the Revolutionary War's Benedict Arnold. The fortuitous capture of a British spy foiled Arnold's plot to betray the Continental Army position at West Point to the British. Arnold committed treason for money and rank in the British Army, and his treachery put American soldiers and the war effort at risk. Hasan's treason employed terrorist tactics. Sure, the lawyers can argue Hasan attacked soldiers, with civilians as incidental targets, and the assault occurred on a military post, but the tactics are those used by jihadis in Afghanistan, Pakistan, Bangladesh, Saudi Arabia, Kenya, Indonesia and a score of other nations -- the armed killer entering an open facility and massacring unarmed men and women.
As a former US Marine, I take that question very seriously, I too once swore an oath to protect and defend the Constitution of the United States. Try him under the Uniform Code of Military Justice and if he is found guilty...hang him in a public ceremony. Furthermore, that execution should be broadcast world wide. That is the message we need to send to those who would undertake Jihad against the United States. It's long past time to follow the wisdom of Theodore Roosevelt,
"Speak softly and carry a BIG STICK"!!!
More importantly, those who would wage war against us, need to understand that we are not afraid to wield that stick upon those who would war against us