 In 2005 , American historian Sahr Conway @-@ Lanz reported his discovery of a declassified document at the National Archives , in which the United States Ambassador to Korea in 1950 , John J. Muccio , notified the State Department , on the day the No Gun Ri killings began , that the U.S. military , fearing infiltrators , had adopted a policy of shooting South Korean refugee groups that approached U.S. lines , after firing warning shots . Pressed by the South Korean government , the Pentagon eventually acknowledged that it deliberately omitted the Muccio letter from its 2001 report . 
