WASHINGTON — The suspect in the killing of 12 people at the Washington Navy Yard on Monday test-fired an AR-15 assault rifle at a Virginia gun store last week but was stopped from buying one because state law there prohibits the sale of such weapons to out-of-state buyers, according to two senior law enforcement officials. Instead, the suspect, Aaron Alexis of Texas, bought a law-enforcement-style shotgun — an 870 Remington pump-action — and used it on Monday as... (GunPolicy.org)