KHARTOUM, Sudan - An American diplomat and his driver were shot to death Tuesday in the Sudanese capital, the U.S. Embassy said, a day after a joint African Union-United Nations force took over peacekeeping in Sudan's Darfur region. It was not immediately known if the motive for the attack was political or a random crime. "This afternoon, the American officer succumbed to his injuries and passed away," said Walter Braunohler, the spokesman at the U.S. Embassy in Khartoum. Braunohler said the diplomat, whose name was not released, worked for the U.S. Agency for International Development. The Sudanese Foreign Ministry identified...