The Washington Navy Yard shooting occurred on September 16, 2013, when 34-year-old Aaron Alexis fatally shot 12 people and injured three others in a mass shooting at the headquarters of the Naval Sea Systems Command inside the Washington Navy Yard in southeast Washington, D.C. The attack took place in the Navy Yard's Building 197; it began around 8:16 a.m. EDT and ended when police killed Alexis around 9:25 a.m. It was the second-deadliest mass murder on a U.S. military base, behind the 2009 Fort Hood shooting. Wikipedia