I don’t think he thought the ammo would add extra umph to his IED. I think the IED was just an extra take ‘em all out, as many as he could. The looped Techno music was an added draw. Kill as many as he could, if they entered his lair.
If he made it out of the main shooting alive and psyched, he could return home and there would be ammo for more kills.
I think his idea worked a little bit like Thanksgiving dinner.
Either you fix the dinner and fret about not making enough or you see all this food that you want. He bought ammo like that.
You think you can put ‘just a dab’ of this and that— next thing you know your plate is crazy full and you can NEVER eat all you have loaded onto your plate.
Or... you are giving away all your containers for carry-homes lest you end up stuffing your fridge to the gills with left-overs.
Why did he strip off his protection at the exit door and then wait at his car nearby? I think he filled his plate too full with ideas and evil and he was not equipped to deal with.
I think he is sick but he is not insane.
I'm not so sure he's crazy. And if he's acting nutty in prison, it may just be an act to try to get off on an insanity plea. This is an arrogant loner who didn't think he needed anybody, because he believed he was superior to everybody. But his vision of himself was out of synch with reality where he was desperate enough to post online personal ads to get sex (this is a last resort for men who have no other options), where he couldn't get a job or the job he thought he deserved, and where he may have been having problems in school.
He concluded that the only way to get himself the "respect" he thought he was due was to stage this very elaborate attack at the most high-profile event where he could pull it off, the biggest midnight movie opening perhaps in history, something sure to draw nationwide media coverage. Because he believes other human beings are inferior to him, it makes no difference to him if this plan required other people to die. Proving to the world and himself that he had what it takes to have power and control over other people was worth more to him than whatever personal consequences for him that could come from this.