A Border Patrol agent shot and killed a man who threatened him with a softball-sized rock at the border, the agency said Tuesday. The agent fired an M-4 assault rifle at the man, who had escaped from a scuffle with another agent as he tried to run back into Mexico, said Border Patrol spokesman David Kim. The victim, whose name, nationality and immigration status were not released by U.S. authorities, was pronounced dead from one bullet wound at El Centro Regional Medical Center after the incident Monday. Kim said he did not know where the man was struck. Pablo Arnaud...