An Afghan police officer shot and killed three U.S. Marines after sharing a meal with them before dawn Friday and then fled into the desolate darkness of southern Afghanistan, the third attack on coalition forces by their Afghan counterparts in a week, AP reported. Thirty-one coalition service members have now died this year at the hands of Afghan forces or insurgents disguised in Afghan uniforms, according to NATO - a dramatic rise from previous years. The assaults have cast a shadow of fear and mistrust over U.S. efforts to train Afghan soldiers and police more than 10 years after the U.S.-led invasion to topple the Taliban's hardline regime Friday's deadly shooting took place in the volatile Sangin district of Helmand province, said U.S. military spokeswoman Maj. Lori Hodge. A U.S. Defense Department official confirmed that the dead Americans were Marine Special Operations Forces. Sangin's district chief and the Taliban both identified the gunman as Asadullah, a member of the Afghan National Police who was helping the Marines train the Afghan Local Police. -- SPA