a little like a LEGO or a k’nex block. But this one-inch piece of plastic is killing people,” said Leigha Simonton, the U.S. attorney for the Northern District of Texas. “Machine gun ...

and are about the size of a small Lego brick. When added to a pistol, the weapon can be fired like a machine gun, which has been prohibited under federal law since the gangster era of Al Capone.