When he shot up the Aurora movie house, he was dressed as a black bloc member dresses. The new batman movie had an OWS type guy as the villian and was dressed in black. The probably mentally unstable Holmes may have been really pissed off at the movie and wanted revenge: explanation here.
This is certainly circumstantial, but it is more plausible than Brian Ross's view that a James Holmes of the Tea Party -- who was not the James Holmes who was the shooter -- performed the mass murder.
I’m reading he purchased ammo on the internet. I’d think he’d have to have a credit card for that.