150702-N-ED767-101 WASHINGTON, D.C. (July 2, 2015) Emergency and law enforcement vehicles block M Street in SE Washington, D.C. in front of the Washington Navy Yard. The Navy Yard, located less than a mile south of the U.S. Capitol, was placed on lockdown following an unconfirmed report of an active shooter. (U.S. Navy photo by Oscar Sosa/RELEASED)