Two U.S. soldiers were shot and killed by a member of Afghanistan's intelligence service, the Afghan National Directorate for Security, officials said. Investigators said the intelligence official, who was off duty at the time of the shooting Saturday morning, was killed when another soldier returned fire, the BBC reported. Officials said the soldiers were accompanying a Provincial Reconstruction Team when the NDS official stopped them. An argument apparently broke out, resulting in the shootings. The incident happened in Panjshir valley, north of Kabul. The NDS officer was a bodyguard for Afghanistan's deputy intelligence chief. The names of the dead soldiers weren't immediately available.