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… - Richard A. Oppel, Jr.

Newtown. San Bernardino. Las Vegas. Sutherland Springs. And now, Parkland. Five of the six deadliest mass shootings of the past six years in the United States. In each of them, the gunman had an AR-15-style semiautomatic rifle.

A vast majority of guns used in 19 recent mass shootings were bought legally and with a federal background check. At least nine gunmen had criminal histories or documented mental health problems that did not prevent them from obtaining their weapons.

The man accused of the Pittsburgh synagogue shooting, Robert Bowers, legally purchased the guns he used to kill 11 people in what is believed to be the deadliest attack against the Jewish community in the United States, according to the federal authorities.
Officials have said Mr. Bowers used four guns — an AR-15 assault rifle and three Glock .357 handguns — in his shooting spree at the Tree of Life synagogue in Pittsburgh on Saturday morning.
An investigation has concluded that the guns were “acquired and possessed legally by Bowers,” the Philadelphia office of the Bureau of Alcohol, Tobacco, Firearms and Explosives said on Tuesday.
Mr. Bowers did not fall into any category barred from gun ownership under federal law, including felons, convicted domestic abusers, dishonorably discharged veterans, or people adjudicated to be mentally ill or subject to certain restraining orders.