Up until that point, the country’s deadliest mass shooting had occurre — SIG MCX

"These AR-15 style rifles have appeared in some of the deadliest shootings in the past few years, including a concert in Las Vegas, a nightclub in Orlando, a church in Texas and an elementary school in Newtown, Conn."

"Not just another AR, but an entirely new rifle platform and complete weapons system - fully configurable for any scenario or environment."

"Among the six deadliest mass shootings in the last six years, the only one not carried out with an AR-15 style rifle was the Orlando nightclub attack two years ago that left 49 dead. The gunman, Omar Mateen, had a Sig Sauer MCX semiautomatic rifle, which shares features with the AR-15, though it functions via a different semiautomatic design — and is just as deadly. All of these military-style semiautomatic weapons have something else in common. They have been heavily marketed as home-defense and marksmanship weapons, and their sales have been a major driver of profits for gun manufacturers over the past two decades."

"When Omar Mateen embarked on his deadly rampage at a gay nightclub in Orlando early Sunday, he carried an assault-type rifle called a Sig Sauer MCX, law enforcement sources tell NPR. The MCX is described by its manufacturer as "the ultimate modern hunting rifle" that is "engineered from the ground up to be short, light and silenced." It is similar in appearance and lethality to the AR-15, the name given to a very popular family of rifles made and sold by nearly two dozen companies. Law enforcement sources call the MCX an "AR-15 equivalent made by a different manufacturer." ... Despite its similarities, the MCX is also fundamentally different from an AR-15. Its internal operating system — its method of propelling bullets from its chamber and cycling to the next round — works differently, and several gun experts contacted by NPR say they do not consider it to be part of the large family of AR-15 rifles."

"While aesthetically similar to and just as lethal as an AR-15, the MCX is internally a different beast, thus all but removing it from the AR-15 family of rifles. Yet while the weapon is different, the MCX and the AR-15 share the same design purpose: providing a highly portable, customizable, easy to operate and accurate rifle for the individual who possesses it."

"Here is a list of mass shootings in the U.S. that featured AR-15-style rifles during the last 35 years, courtesy of the Stanford Geospatial Center and Stanford Libraries and USA TODAY research:... June 12, 2016: Omar Mateen, 29, used an AR-15 style rifle (a Sig Sauer MCX), and a 9mm Glock semi-automatic pistol to kill 49 people and injure 50 at an Orlando nightclub before he was killed."