Well, to be completely honest, I don't know all of the ins-and-outs of the interplay of jurisdiction between State, Federal, and in-State locations under Federal supervision.
Normally, if a solder commits an offense on-post, whether it be against another soldier or a civilian, the Army takes jurisdiction. If a soldier commits an offense off-post, the State gets to make first call if they want to prosecute or not. Depending on the status of the "victim" (was it another soldier, a civilian, or an off-post business), the severity of the crime, and how the County/City prosecutor views the outcome in civilian court versus the possible result in military court, the State will either keep or surrender jurisdiction.
Now, since the offense took place on post and was committed by a soldier, my guess is that the State wasn't given the option of asserting jurisdiction. If the "civilian" victims of the shooting had any connection with the military .. such as being a retiree, an on-post civilian employee, a dependent wife or husband .. that bolsters the military's assertion of jurisdiction.
Now, that doesn't necessarily negate the possibility of civil court action against MAJ Hasan for the killings. I am out of my league there. I was a military court reporter for 18 years (having been an infantryman/M60 gunner for my first three years in the Army until my promotion to SGT) and have been the civil service court installation court reporter on Fort Hood since 1994. My expertise, such as it is, is strictly within military court parameters.
I have no experience with military courts.
But the actions of the court clearly tell me that this is not just another case. It is being directed by political forces. Those are coming through the chain of command from the White Hut and the Liar-in-Chief.
This is not how military justice is normally handled.
Makes me wonder if there is a political connection between Obozo and Hassan that has not previously been exposed. He was on the transition team, what else?