More info:
Apparently the suspect was actually a fairly intelligent science student from San Diego, where his neighbors remember him as a "clean-cut, studious young man of sparing words", and the guns used in the shooting were purchased legally.
On a less sane note, he was also reported to, after being approached by the police, claim to be The Joker, and some rumor he was dressed as Bane, from the description of his attire.
