Five blasts confirmed this weapon is as reliable and accurate as advertised. All I could think about was what it would be like to be on the other end, at a church, a nightclub, or a concert; or at a school, where children are the target and the shooter is feet, not yards away. At Sandy Hook Elementary School, one of three recovered firearms was a Bushmaster XM15-E2S rifle. At Stoneman Douglas High School in Parkland, Fla., the shooter used an AR-15. The hotel suite used by the Las Vegas gunman last fall to kill 58 concertgoers contained an arsenal of 23 weapons and accessories, including semiautomatic rifles, scopes, and hundreds of rounds of ammunition.