An American soldier shot and killed an Afghan guard at a base in the country's north, apparently because the American thought the guard was about to attack him, Afghan police said Sunday. Friday's shooting in Sari Pul province in northern Afghanistan resulted from an unfortunate misunderstanding, said Sayed Jahangir, the deputy police chief for the province. U.S. forces were "aware of an incident in northern Afghanistan" and were investigating, said U.S. military spokesman Lt. Col. Jimmie Cummings, according to a report of the Associated Press.