An Afghan soldier shot to death a 22-year-old Marine at an outpost in southwestern Afghanistan last month. This is a previously undisclosed case of an apparent Afghan turncoat. It’s at least the seventh killing of an American military member by his supposed ally in the past six weeks according the Marines. Lance Cpl. Edward J. Dycus of Greenville, Miss., was shot in the back of the head on Feb. 1 while standing guard at an Afghan-U.S. base in the Marja district of Helmand province.