No way to know, as yet, but according to the media, he was a registered Democrat. What happened to the assertion by ABC that he may have been a member of the Tea Partry? Oh, they were so wrong again! ABC has a habit of being 180 degreees away from the truth.
I think this man's frame of mind is one that obcessed with the Batman characters,...most especially the Joker. I think he became suffused with anticipation of the latest rendition of the Batman movie, and as he did he obcess, pathologically, with the Joker (specifically the Heath Ledger rendition). Over the past 2 months or so he became so obcessed he decided to live out that Ledger character. His obcession degenerated to a point where he could not discern reality from his obcession with the Joker. Remember in the movie the Joker began with a takedown of the bank. This was a very violent movie with a lot of killing depicted...specifically shot by guns. Then as he was in jail, near the end, explosions went off...the DA was injured....The Joker was not through even as he sat in prison.....just like our Aurora Joker, he was still blowing up things and people.
When he was apprehended behind the theater, the police asked him who he was,...he said, "I am the Joker." The authorities need to look at the movie again.