{Afghanistan policeman kills 3 American troops in Helmand province|Gen|(CBS/AP) KABUL, Afghanistan – An Afghan police officer shot and killed three U.S|Friday’s deadly shooting took place in the volatile Sangin district of Helmand province, said U.S|Sangin was a Taliban stronghold for years and has one of the highest concentrations of improvised explosive devices, or IEDs, in the country|The U.S|”Investigations have determined that a large majority of green-on-blue attacks are not attributable to insurgent infiltration of the ANSF (Afghan National Security Forces), but are due to isolated personal grievances against coalition personnel,” the report said.