The type of AR-15 rifle that terrorist Omar Mateen used to kill 49 people and wound dozens more at a nightclub in Orlando has become the weapon of choice for mass murderers in the U.S. and is one of the common links between the shootings.
Even though it has caused carnage and left dozens of people dead in multiple shootings this decade alone, the military-inspired semi-automatic rifle designed for civilian use is perfectly legal in most states.
There were calls for a nationwide ban after the same type of firearm - capable of firing dozens of rounds in less than a minute without being reloaded - was used in the Sandy Hook school shooting, but it remains readily available at gun shops and was purchased just last week by Mateen before he went on his killing spree.
Mateen, 29, was armed with a .223-caliber AR-15-type rifle and a 9mm semi-automatic pistol – both legally purchased – when he opened fire at the Pulse gay club in Orlando early Sunday morning.
Called a ‘killing machine’ or 'weapon of war' by those who want to see it banned, the AR-15 rifle is the civilian version of the fully-automatic M16 used by soldiers in the Vietnam War. Unlike the M16, users must pull the trigger every time they want to fire a shot.
When it is used against humans it is intended to cause maximum carnage in a brief amount of time, said experts.
'It was designed for the United States military to do to enemies of war exactly what it did [in Orlando]: kill mass numbers of people with maximum efficiency and ease," said lawyer Josh Koskoff, who is representing families of the Sandy Hook victims in a lawsuit, in an interview with the New York Daily News.
Richard Frankel, an ABC News contributor and former counterterrorism special agent for the FBI, told the TV network that mass shooters may be choosing the AR-15 because it is easy to operate and easy to obtain, as it’s sold by many gun retailers in the U.S.
‘It’s easy to load, point and shoot,’ he said, adding that an AR-15 can hold 30 rounds at a time and fire off those rounds in less than a minute.
A database compiled by Mother Jones magazine found that AR-15 rifles have been used in at least 10 mass shootings since 2011, Reuters reported.
The National Shooting Sports Foundation, which represents gun manufacturers, said there are five million to 10 million AR-15 rifles in the U.S., a small percentage of the 300 million firearms owned by Americans.
Last October, gunman Chris Harper-Mercer, 26, used an AR-15-style firearm to kill nine people before he killed himself at Umpqua Community College in Roseburg, Oregon.
An AR-15 model was used by married couple Syed Rizwan Farook, 28, and Tashfeen Malik, 29, when they killed 14 people and wounded nearly two dozen others at a work Christmas party in San Bernardino, California, last December.
Police recovered two .223-caliber AR-15-type semi-automatic rifles after the couple died in a shootout with officers.
An AR-15-type firearm was used by 20-year-old Adam Lanza in the Sandy Hook Elementary School shooting in Newtown, Connecticut, which shocked the nation in December 2012.
Lanza fatally shot his mother, Nancy, who legally obtained the firearms, at their home before he killed 20 children and six adult staff members at the school.
That shooting renewed the gun debate in the U.S. and led to calls for a ban on sales of AR-15-type firearms.
However, sales went through the roof.
