So, I’ve figured out why the guy shot up the theater. Nolan ripped off Moore’s joker from The Killing Joke- without including the characters critical backstory (society broke him and drove him insane). In the story, Batman himself acknowledges that society has failed- but still seeks to protect human life. The Joker drugs him and throws him in to a demented amusement park ride designed to traumatize and poison his mind with a narrative of despair- but Batman successfully fights off the drugging, and saves the day.
Unfortunately in Nolan’s new conceptions, society becomes an essentially passive Other, as in Hitchock- society is unaware, essentially innocent of any problems. Rather than complicit, as in Moore.
So being too in to Nolan’s movie + hating society = shooting up that fucking theater! He couldn’t be the Batman- because he felt alienated from society- so he felt he had to embody the Joker, and go do ultra-violent Joker stuff.
Alan Moore’s potent anarchist psychomagic was corrupted- and unfortunately the viewing experience was for that guy was something the Joker would have intended for him.
So basically, this is all Christopher Nolan’s fault.