I love it when EVERYONE'S WRONG! They're not domestic terrorists or Arabs, but Chechens who have been here for a while. And apparently they've picked up some paramilitary training along the way.
Their operation can't have been too well planned or financed, though. Robbing a convenience store is a pretty bush-league move. And car-jacking a getaway vehicle, and telling the victim they're the marathon bombers, seems like a pretty dumb thing to do, too.
