The gunman, Devin Kelley, bought his Ruger AR-15 legally after the Air ... available accessory is the trigger crank, which allows the shooter to spin a mechanism attached to the trigger like ...

The device, also known as a "gat crank," can sell for as little ... converting its firing mechanism to that of an assault rifle, and therefore rendering it faster and more dangerous—but also ...

A source familiar with the case told CNN that the possibility of modifications to the firing mechanism of the gun was learned by the special prosecutors overseeing the case in New Mexico.