ACAPULCO, Mexico — A Mexican soldier said that a U.S. citizen attacked an army convoy and was killed when troops shot him in self-defense outside the resort city of Acapulco, a police official said. The man's father said Monday that he found it hard to believe. An army lieutenant told police that Joseph Proctor opened fire on a military convoy with an AR-15 rifle, forcing the soldiers to shoot back, said Domingo Olea, a police investigator in the western state of Guerrero, where Acapulco is located. Olea provided no further details on Proctor, who was found dead in his car...