A law enforcement official says the FBI is investigating the possibility that the fatal shooting of a U.S. border patrol agent and the wounding of another was a case of friendly fire. The official says the probe is looking into whether the two men exchanged gunfire Tuesday in the mistaken belief that each was being fired on by a hostile gunman. The shooting occurred near Bisbee, Ariz. The official spoke on condition of anonymity because the matter is under investigation. At FBI headquarters, spokesman Chris Allen declined to comment.