The man accused of the Pittsburgh synagogue massacre—the deadliest anti-Semitic attack in U.S. history—legally purchased all the firearms he used to kill 11 worshippers last Saturday morning, federal authorities said. Robert Bowers is believed to have used four guns in the attack: one AR-15 assault rifle and three Glock .357 handguns. An investigation found the guns were “acquired and possessed legally by Bowers,” the Philadelphia office of the Bureau of Alcohol, Tobacco, Firearms and Explosives said Tuesday. Felons, convicted domestic abusers, dishonorably discharged veterans, and people adjudicated to be mentally ill or subject to certain restraining orders cannot own guns, but Bowers didn’t fall into any category. An ATF spokesperson also said Bowers had a handgun license and is believed to have owned 10 guns in total.