Both here and on The High Road, I've seen posts which refer to the shooter's mental state and his culpability. In one (& I don't recall if it was here or THR), someone said that he might "get off" because of mental disease or defect. One of the oft-overlooked aspects of "not guilty by reason of insanity" is that (at least in Arkansas) one who is found not guilty by reason of mental disease or defect does not just pack up and head home. He gets packed up and sent over to the State Hospital.
I'm a lawyer, but I'm not your lawyer. If you need some honest-to-goodness legal advice, go buy some.