Helicopter Crash Kills 12 NATO Troops in Kabul KABUL, Afghanistan - A Turkish helicopter crashed into a house in Kabul on Friday, killing at least 12 NATO service members and two civilians, the American-led coalition and Afghan police said. The crash destroyed much of the three-story house in the eastern part of the city, and police and firemen were digging through the rubble, said Saifuddin Nangeyali, the police chief of the area where the apparent accident took place. He said that another Afghan civilian was injured along with the two killed in the crash. The coalition said in a statement that the cause of the crash was under investigation. But it did say there was no insurgent activity in the area when the helicopter went down. The helicopter was operated by a private Turkish company, The Associated Press reported, although it was not clear if all the dead were Turks. If the dead were Turkish service members, it would represent the largest loss of life for Turkey in Afghanistan. Meanwhile, military officials said a 22-year-old Marine killed last month at an outpost in the southwestern province of Helmand was shot in the back of the head by an Afghan soldier - the seventh reported death of an American at the hands of Afghan service members in the past six weeks, according The A.P. The Marine, identified as Lance Cpl. Edward J. Dycus , was killed on Feb. 1 while standing guard at an outpost in the Marja district, The A.P. said, citing Marine officials who requested anonymity because the matter is under investigation. Marja was the scene of a large-scale coalition and Afghan operation against the Taliban two years ago, and the outpost where Corporal Dycus was killed is shared by American and Afghan forces. The coalition said it could not immediately comment on The A.P. report.Once portrayed as a manageable problem by coalition commanders, Afghan soldiers are now killing their coalition counterparts at what officials consider an alarming rate. The attacks have raised serious concerns about a major element of the American strategy in Afghanistan - training Afghan units to take over the fighting against the Taliban by partnering the directly with coalition forces at bases and on the battlefield. Some of the killings are thought to be the work of Taliban infiltrators. But most are believed to stem from the deep animosity between Afghan and foreign forces. The problem has been magnified by a recent string of American actions, including this month's shooting of 16 Afghan civilians in a door-to-door rampage by an American soldier in Kandahar Province, also in southern Afghanistan. The A.P. said that the Dycus family has been notified that their relative was killed by an Afghan soldier, although the death had not previously been characterized as such publicly. Instead, the Pentagon said the day after Corporal Dycus died that he was killed "while conducting combat operations."