Stephen Paddock: Las Vegas shooter used legal 'bump stock' on 12 guns to make them fire like automatics

Renewed calls for device to be outlawed after 58 people were killed at music festival

Images from inside Stephen Paddock's hotel room show a number of assault rifles (ABC News )

Las Vegas gunman Stephen Paddock used a lethal but legal device to turn his rifles into even deadlier weapons, according to US law enforcement officials.

The killer gunned down 58 people and injured more than 500 after opening fire on a music festival from the 32nd floor of Sin City's Mandalay Bay hotel.

He is now known to have used a bump-stock to turn his semi-automatic rifles into virtually automatic ones, meaning bullets are fired in a steady stream for as long as the trigger is held.

The device uses the recoil from the gun to keep the trigger constantly pressed down, allowing bullets to be fired consecutively. While automatic weapons are mostly illegal in the US, bump-stocks are lawful because technically they still require the shooter to press down on the trigger each time.

Law enforcement officials have said Paddock fitted a bump-stock to 12 of the weapons found in his hotel room.

Jill Snyder, the special agent in charge of the investigation for the Bureau of Alcohol, Tobacco, Firearms and Explosives, confirmed that Paddock had used the devices.

Despite making weapons much more deadly, bump-stocks can be bought in the US for just $100 (£75).

Ms Snyder said: “Bump fire stock, while simulating automatic fire, do not actually alter the firearm to fire automatically, making them legal under current federal law.”

Investigators have seized a total of 42 weapons owned by Paddock, 23 were found in his hotel room and a further 19 at his home in Mesquite, a small town around an hour from Las Vegas.

The impact of the bump-stock led people at the concert to think the gunman had an automatic weapon.

One, Megan Kearny, told NBC News: “All of a sudden we heard what sounded like a machine gun and people just started screaming that they were hit and to get down.

“About every 20 seconds after that you would hear a round of machine guns, and people just dropping, hundreds of bodies over the ground.”

Democrat senator Dianne Feinstein has previously campaigned for bump-stocks to be banned and said she would bring forward legislation to that end.

In the wake of the Las Vegas attack, she wrote on Twitter: “Automatic weapons are illegal, but individuals are still able to purchase bump stocks to allow semi-automatic weapons to fire up to 800 rounds per minute—the rate of automatic weapons—and inflict maximum carnage.

“I’m looking at ways to proceed with legislation to ban bump fire stocks and close this ridiculous loophole for good. Doing nothing in the wake of this tragedy is not an option.”