Troops, one with a machine gun, stand guard on the steps of the U.S. Senate wing of the Capitol Building in Washington, D.C., April 5, 1968. Federal troops were called into the nation's capital by order of President Lyndon Johnson during a day of arson and looting following the assassination of Dr. Martin Luther King, Jr. in Memphis, Tenn., April 4. The flag is at half staff in tribute to the civil rights leader.
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