When Omar Mateen entered an Orlando nightclub to carry out the deadliest mass shooting in US history, he wielded a weapon that has been used in massacres from California to Connecticut: a military-inspired semi-automatic rifle.
Though so-called assault rifles account for a small fraction of the US’s 30,000 annual gun deaths, they have been used in at least 10 mass shootings since 2011, according to a database compiled by Mother Jones magazine.
The prevalence of these firearms has made them a focal point in the debate over US gun laws, as opponents say civilians should not own what they describe as “weapons of war”.
Backers say they are simply modern rifles enjoyed by millions of law-abiding Americans.
Law enforcement officials say Mateen carried an AR-15 style assault rifle and a handgun when he killed 49 people and wounded 53. He also had an unidentified device, Orlando Police Chief John Mina said.
The AR-15 was developed from the US military’s M-16 rifle, used in the Vietnam War in the 1960s.
Unlike the military version, the AR-15 is not fully automatic, meaning users must pull the trigger each time they want to fire a shot. Like the military version, many AR-15s combine light weight with a relatively modest recoil.
Prominent manufacturers include Smith & Wesson, Sturm Ruger and Remington Arms Co, which faces a lawsuit from some families of Sandy Hook school shooting victims who say the rifle should not be sold to civilians.
“It is the gold standard for killing the enemy in battle, just as it has become the gold standard for mass murder of innocent civilians,” Josh Koskoff, a lawyer involved in the case, said.