Fact check: AR-15 style rifles used in 11 mass shootings since 2012

Corrections & clarifications: An earlier version of this story incorrectly referenced the legality of machine guns in the United States. Machine guns registered with the ATF before 1986 can still be bought and sold with government approval.

The claim: AR-15 rifles were used in 12 recent mass shootings

Just as it has for other widely publicized incidents in the United States, debate about gun control legislation has followed the news of mass shootings in Atlanta and Boulder, Colorado. The events left 17 Americans dead.

A central question in the debate has been whether to ban assault weapons, defined in the 1994 Federal Assault Weapons Ban as certain semi-automatic firearms and high-capacity ammunition magazines.

Shortly after news broke of the shooting at a grocery store in Boulder, Twitter user Adam C. Best, a progressive activist and founder of the sports site FanSided, posted a tweet that associated the AR-15 rifle with 12 high-profile mass shootings in the last 10 years. The tweet was soon posted to Facebook; one post received over 2,400 reactions and 1,600 shares.

Best's claim is mostly accurate: All but one of the shootings involved the use of at least one AR-15-style assault rifle. However, as we explain below, in several cases shooters had multiple guns — including 23 in the case of the Las Vegas gunman.

USA TODAY reached out to Best for comment. A Facebook page that reposted the tweet, Alexandria Ocasio-Cortez Fans, said it was under the impression that the tweet was true.

What is the AR-15, and how is it different from other popular firearms?

An AR-15 is a type of semiautomatic, or "self-loading," assault rifle.

As defined in U.S. law, the term "semiautomatic," as opposed to "automatic," means the gun's operator must pull the trigger to fire each shot. NPR outlined its most recognizable features: it automatically reloads after each shot and holds around 30 bullets before an operator needs to reload the gun.

Dubbed "America's Rifle" by the NRA, the AR-15 is popular for its easy-to-modify design and lack of recoil or "blowback" after firing, which preserves the operator's aim and makes the shot more precise, as The Washington Post detailed in a Q & A on the firearm.

While the AR-15 is not a machine gun, a user can modify the AR-15 to approximate the function of an automatic gun by attaching a device called a "bump stock", as was the case in the Las Vegas shooting.

Soon after the mass shooting at Marjory Stoneman Douglas High School in Parkland, Fla. in February 2018, the Trump administration took action against bump stocks. The ATF issued a rule that changed the definition of "machine gun" to include bump stock devices, therefore rendering them illegal to possess. However, the U.S. Court of Appeals for the Sixth Circuit put a hold on the ban in March because it could be unconstitutional, in a lawsuit filed by Gun Owners of America, Inc., Bloomberg Law reported. The future of the ban remains uncertain.

(Weapons in the machine gun category cannot be manufactured for civilian use in the United States, though a 1986 law still allows fully automatic weapons registered with the ATF before 1986 to be bought and sold, after paying a fee and submitting an application and other paperwork.)

In this June 24, 2016 photo, an AR-15 is held in Auburn, Ga. (AP Photo/Lisa Marie Pane, File)
In this June 24, 2016 photo, an AR-15 is held in Auburn, Ga. (AP Photo/Lisa Marie Pane, File)

The Washington Post and NPR trace the history of the modern AR-15 back to the 1950s, when its original manufacturer ArmaLite (now Colt) created the M-16 machine gun. The M-16 became standard issue for American troops fighting in the Vietnam War.

After the war, the company named a semiautomatic version after itself (AR stands for "ArmaLite Rifle," not "assault rifle") and marketed it to the public. Because the original patent has expired, the AR-15 is now the generic name for many variants created by a variety of firearms makers.

Weapons used

USA TODAY researched each shooting that Best mentioned and found that in 11 out of 12 of the incidents listed, AR-15-style rifles were used. The sole exception is the Orlando Pulse Nightclub shooting, in which the shooter used an assault rifle that is not considered an AR-15 variant.

In the list below, we detail the weapon or weapons used in each shooting, in addition to the number of victims and their dates. Click on the headers for more information about the incidents from USA TODAY.

Boulder, Colorado (King Soopers grocery store)

  • Date: March 10

  • Lives lost: 10

  • Weapon used: Ruger AR-556 pistol

The Washington Post reported that the prime suspect in the shooting, Ahmad Al Aliwi Alissa, purchased a Ruger AR-556 pistol on March 16, just four days after the state of Colorado's two-year assault weapons ban was blocked in court.

Orlando, Florida (Pulse nightclub)

Jillienne Riethmiller, left, and Zachary Guadalupe spend time at the memorial set up for the shooting victims at Pulse nightclub where the shootings took place. On June 12, 2016, a mass shooting took place at Pulse nightclub killing 49 people and wounding 53 in one of the worst mass shootings in U.S. history.
Jillienne Riethmiller, left, and Zachary Guadalupe spend time at the memorial set up for the shooting victims at Pulse nightclub where the shootings took place. On June 12, 2016, a mass shooting took place at Pulse nightclub killing 49 people and wounding 53 in one of the worst mass shootings in U.S. history.
  • Date: June 12, 2016

  • Lives lost: 49

  • Weapon used: Sig Sauer MCX

The Sig Sauer MCX is marketed as a "modern sporting rifle" and is very similar to the AR-15 in form and function. However, as explained in a Slate analysis, it is not an AR-15 variant because it uses a gas piston system to propel bullets from within the gun instead of a direct impingement system. It is also more modular, so parts can be switched out and customized more easily, says Tactical Life magazine.

Parkland, Florida (Marjory Stoneman Douglas High School)

A woman sits at a sign for Marjory Stoneman Douglas High School in Parkland, Florida.
A woman sits at a sign for Marjory Stoneman Douglas High School in Parkland, Florida.

Las Vegas (Highway 91 country music festival)

In this Oct. 4, 2017, file photo, shooting instructor Frankie McRae demonstrates the grip on an AR-15 rifle fitted with a "bump stock" at his 37 PSR Gun Club in Bunnlevel, N.C. The devices were used by Stephen Paddock when he opened fire on a country music festival in Las Vegas, killing dozens of people.
In this Oct. 4, 2017, file photo, shooting instructor Frankie McRae demonstrates the grip on an AR-15 rifle fitted with a "bump stock" at his 37 PSR Gun Club in Bunnlevel, N.C. The devices were used by Stephen Paddock when he opened fire on a country music festival in Las Vegas, killing dozens of people.
  • Date: Oct. 1, 2017

  • Lives lost: 58

  • Weapons used: 23 different weapons were recovered in the gunman's hotel suite, including multiple AR-15 style rifles and hundreds of rounds of ammunition, USA TODAY reported.

Several of the AR-15 variants used in the Las Vegas shooting had a bump stock attached, which allows guns to fire roughly as rapidly as a machine gun.

Aurora, Colorado (Century 16 movie theater)

People gather outside the Century 16 movie theater in Aurora, Colo., at the scene of a mass shooting early Friday morning, July 20, 2012.
People gather outside the Century 16 movie theater in Aurora, Colo., at the scene of a mass shooting early Friday morning, July 20, 2012.
  • Date: July 20, 2012

  • Lives lost: 12

  • Weapon used: One AR-15 variant from Smith & Wesson, a pump-action 12-gauge shotgun and at least one .40-caliber semiautomatic pistol, according to The New York Times.

Sandy Hook Elementary School (Newtown, Connecticut)

Waffle House (Nashville, Tennessee)

Members of the Billy Graham Rescue Response Team pray with Lancelot DeSilva, second left, Susan Cox, third from right, and Valerie Aaron, right, at a memorial outside the Antioch Waffle House for the four people killed by a gunman on April 25, 2018.
Members of the Billy Graham Rescue Response Team pray with Lancelot DeSilva, second left, Susan Cox, third from right, and Valerie Aaron, right, at a memorial outside the Antioch Waffle House for the four people killed by a gunman on April 25, 2018.

San Bernadino, California (holiday office party at Inland Regional Center):

  • Date: Dec. 2, 2015

  • Lives lost: 14

  • Weapon used: Two AR-15 variants (Smith & Wesson M&P assault rifle and a DPMS Panther Arms assault rifle) a Smith & Wesson handgun and a Llama handgun, according to The New York Times.

Scene outside the Cinergy movie theater in Odessa, Texas where a gunman was killed in a shootout with police.  Five people were killed and 21 people were injured in a shooting on Saturday, Aug 31, 2019 in Odessa and Midland, Texas.
Scene outside the Cinergy movie theater in Odessa, Texas where a gunman was killed in a shootout with police. Five people were killed and 21 people were injured in a shooting on Saturday, Aug 31, 2019 in Odessa and Midland, Texas.

Midland/Odessa (West Texas cities)

Poway synagogue (near San Diego)

Sutherland Springs (rural Texas church service)

Tree of Life Synagogue (Pittsburgh)

Les Wexner speaks at a prayer vigil held at the Jewish Community Center of Greater Columbus on Sunday, October 28, 2018, for the victims of the Tree of Life Synagogue shooting in Pittsburgh.
Les Wexner speaks at a prayer vigil held at the Jewish Community Center of Greater Columbus on Sunday, October 28, 2018, for the victims of the Tree of Life Synagogue shooting in Pittsburgh.

More: Suspect charged with 29 counts in 'horrific' synagogue shooting in Pittsburgh

Our rating: Missing context

We rate this claim MISSING CONTEXT, because without additional information it could be misleading. All but one of the shootings involved the use of an AR-15-style assault rifle, and the shooting that did not use an AR-15 used a very similar assault rifle. However, the lack of context could lead a reader to believe that the shooters in all incidents listed only used an AR-15, when in several cases they had multiple guns — including 23 in the case of the Las Vegas gunman.

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This article originally appeared on USA TODAY: Fact check: Post missing context about AR-15 rifles and mass shootings