Las Vegas shooter used special device on two guns
The gunman who unleashed hundreds of rounds of gunfire on a crowd of concertgoers in Las Vegas attached what is called a 'bump-stock' to two of his weapons, in effect converting semi-automatic firearms into fully automatic ones.
Las Vegas shooter Stephen Paddock, who killed 59 people and injured hundreds more, had 23 guns in his hotel room.
Two officials familiar with the investigation told the Associated Press that Paddock had bump stocks attached to two semi-automatic guns.
A semi-automatic weapon requires one trigger pull for each round fired. With a fully automatic firearm, one trigger pull can unleash continuous rounds until the magazine is empty.
The bump stock basically replaces the gun's shoulder rest, with a 'support step' that covers the trigger opening. By holding the pistol grip with one hand and pushing forward on the barrel with the other, the shooter's finger comes in contact with the trigger.
The recoil causes the gun to buck back and forth, 'bumping' the trigger. Technically, that means the finger is pulling the trigger for each round fired, keeping the weapon a legal semi-automatic.