Two Americans who were shot dead Saturday inside the Interior Ministry in Afghanistan's capital Kabul are believed to be a colonel and a major in the U.S. military, Afghan security sources told Reuters. A spokeswoman for NATO's International Security Assistance Force (ISAF) confirmed two of their servicemen had been shot dead in central Kabul by an individual who turned his weapon on them. She declined to say if the killer was a member of the Afghan military or police.