In the wake of the deadly mass shooting at Pulse, a gay club in Orlando, Sunday morning, Orlando Police Chief John Mina said the Orlando shooter used "AR-15-type assault rifle" when massacring over 50 people, The New York Times reported. As Slate noted in an introduction to an older piece they re-ran Sunday, the AR-15 is the same weapon used at Sandy Hook Elementary in 2012, a shooting that murdered 20 children and 6 adults. The same type of automatic rifle was used in the Aurora, Colorado movie theatre shooting in 2012 that killed 12 people and, as The Trace noted, in the shooting in San Bernardino, California in December that killed 14. All of which left many members of the public confused Sunday about why these weapons are legal and angry that they have not been outlawed.

(Update: The FBI has updated the death toll to 49 victims. The shooter was also killed.)

In the past, gun advocates have argued that AR-15s are designed for hunting, target shooting, and home- and self-defense. In 2013, then NRA CEO Wayne LaPierre legal semi-automatic guns, "They are among the most popular guns made for hunting, target shooting and self-defense." But in the wake of the Pulse shooting, that argument isn't carrying much sway with a mourning and terrified public.

In the aftermath many users expressed outrage that AR-15 type weapons can be lawfully obtained. (Justin Peters, the author of the Slate article, clarified that authorities often refer to these weapons as "AR-15-type" because the AR-15 is the model name of a Colt product.)

Since the Orlando mass shooting is the deadliest in U.S. history, it's possible that Congress will again examine whether semi-automatic assault weapons should be legal. What is unclear is whether that would actually lead to a ban, given the NRA's powerful influence in Washington. After all, 20 children were killed at Sandy Hook, and AR-15s are as readily accessible as ever.