Yeah, the theory is the guy's been in there a few times...from what I heard he was in and out in under 120 seconds, and had a plan that he stuck to. Didn't stop for anything, made a line straight for the .45s (I'm assuming high dollar 1911s?) and the NFA stuff, and exited from there. Didn't touch any of the rifles or anything else.
So it's probable that he's been in a few times...I'd bet the local & state PD, along with the ATF, are pouring over prior surveillance video and looking for anyone who matches. Hopefully they didn't go cheap on that, and kept more than a month's worth...