Just a quick aside, Civilians have always been able to legally purchase semi auto-matic versions of military rifles (i.e. pull the trigger back once, one round is fired) here in the USoA. Civilians can not purchase either fully automatic weapons (i.e. the lead hose), or weapons that may fire of a “burst” of several rounds per trigger pull, without a serious amount of red tape and hoop jumping in the way of licenses that is intended for museums and the like to own and display full military versions of firearms.
It is easy and legal for anyone with a clean background to purchase a semi-automatic ar-15 or ak-47. There are not cheap “pos” but may be made by the government contractors that provide the military with them (such as Colt), by the original designer (Armalite), or by smaller gun manufacturers (like Bushmaster), without having to talk to dark figures from the underworld. I would be surprised if most gun stores did not offer some of these rifles. I could be wrong, but I think Wal-Mart and K-mart quit selling firearms of all types sometime after the assult weapons ban, and the negitive press that it generated.
There are ways of these “semi-automatic” rifles to be fully automatic, of course, but then since the technology behind them is not complex, and widely understood, how could there not be? Anyone with the know-how, and the access to a machine shop, can build all kids of things of questionable legality.
I did not read anything the news article that mentioned that the rifle was a fully automatic one, I would assume that it was a legal, “semi-automatic” one. Since the student is 13 years old, it is illegal for him to purchase any firearm. Unfortunately it is likely that Tricky hit the nail on the head and it was stolen from dad’s gun safe, or someone else that the boy knew.