A sufficiently powerful recurring delusion is all you'd need to really set yourself up for some serious mayhem.
Think about it ~ he had 6,000 rounds of ammunition ~ so, what do you do with it once you've got it? Let's say he had some totally normal moments (a situation much more in line with bipolar disorder), if he were not medicated he might be able to play 'catchup' ~ have worked with some bipolar folks who did just that. Then, outside those moments they preferred to be on zonk medicine of whatever kind they could get a doctor to prescribe, or they'd drink heavily.
If he were bipolar, he'd become aware every now and then that he had 6,000 rounds of ammunition ~ and he'd do something with it.
I'm not ruling out bipolar disorder or borderline, but doggone it, this total absorption into a comic book character really looks like a manifestation of a schizophrenic delusion, or, as I said, he could have a tumor.
BTW that started with a search for FURRIES to see if any of their get togethers also had Batman, Robin, Darth Vader or Empire Troopers ~ and I found one ~ one search led to the next and it's safe to say that it is normal to find folks who own body armor and helmets with gas masks who go to these comic book cons, furry cons, and others ~
I"ve heard sex is commonplace with the costumed geeks.