The guys who owned that gun are linked to Mexico's "Zetas" and no, not the sorority. They tend to cut people's heads off rather than shoot them which may explain the lack of ammo. I was going to post a link to the video, but i didn't want any accidental viewings as it's pretty graphic. If you want to see what these people do, go to google and type "zetas cut head off" click on the "best gore" link and you can see a rival gang member have his head removed with a chainsaw while the other gets his removed with a knife.
I wouldn't want to be the guy sporting that AK after it was removed from their possession.