Here's a perspetive I did not see while I read through this. The perpetrator was a US MARINE...a trained killer. Who's to know how much post-tramatic stress he may be suffering and trying to anesthetize when he finally flipped out in a public place (non-war zone). These men and women go through their own version of hell and are then released into the streets expected to act 'normal'. Go back and look at all the anti-social/sociopathic and often violent incidents that happened after the Vietnam war, then consider what we have to look forward to.
Factor that into your thinking when you deduce to a conclusion.