Going with HH6's doc...this guy had no deployments to Iraq and only one other post? So he has pretty much been at Fort Hood for a very long time. Going deeper, with the new found info this guy isn't the poster child for multi-deployment, extended tour PTSD that the media was probably frothing at the mouth to portray the military as.
Was he being deployed somewhere, though? If so, to which theater and in what capacity? Combat or desk job?
This outburst and attack, had to have outside help/planning etc. Info is shallow and slim but he doesn't fit the profile for wackjob or trigger happy mass murderer. He is educated and hasn't been deployed.