Senate Sergeant at Arms Terrance Gainer

Police tactical units leave after responding to a shooting at the Navy Yard in Washington, D.C., on Sept. 16, 2013. (credit: SAUL LOEB/AFP/Getty Images)

Senate Officials Shut Complex At US Capitol As Authorities Search For Potential Second Suspect

Senate officials shut down their side of the U.S. Capitol complex Monday while authorities searched for a potential second suspect in the Navy Yard shootings.