On September 16, 2013, Aaron Alexis, a lone gunman armed initially with a shotgun, fatally shot twelve people and injured three others in a mass shooting at the headquarters of the Naval Sea Systems Command (NAVSEA) inside the Washington Navy Yard in Southeast Washington, D.C. The attack began around 8:20 a.m. EDT in Building 197. Alexis was killed by police around 9:20 a.m. EDT. It was the second-deadliest mass murder on a U.S. military base after the Fort Hood shooting in November 2009.