One of the guns used by Mateen at the Pulse nightclub was an AR-15 semiautomatic rifle. The gun was also used in the massacres at Sandy Hook Elementary School; the Aurora, Colorado, movie theater; and at the Inland Regional Center in San Bernardino, California. AR-15-style rifles like Mateen’s were once illegal under the Federal Assault Weapons Ban, which expired in 2004.

Presumptive Republican presidential nominee Donald Trump has used the shooting in Orlando to double down on his call for a ban on Muslim immigration to the United States—even though the shooter was a U.S. citizen born in New York.