[SBprone]

It wouldn't make much sense to procure an AK-74. Simple possession of this full-auto rifle means a long stretch in the slammer for anybody caught with one. I don't know of any semi-auto versions that have the external appearance of the military version.

A bolt rifle in .223 is better suited for this kind of terror operation and they are commonplace. Also, 5.45mm bullets are very uncommon and the few types that exist could easily be matched with the recovered bullet fragments by the FBI lab.

[m1911]

Semi auto AK74s are available, I see them in the Shotgun News a lot, along with various ammo. I agree that it's probably not the weapon though, whatever the shooter's motivation and background. I suspect it is an "evil black rifle" for a couple of reasons: It allows the shooter to fantasize about actual combat if that's the brand of sicko we're dealing with, and if it is an ideologically motivated shooter, it will allow him to "take a few with him" when they get him.