HOUSTON — A U.S. Border Patrol agent suspected of killing four women was arrested early Saturday after a fifth woman who had been abducted managed to escape from him and notify authorities, law enforcement officials said, describing the agent as a “serial killer.” Juan David Ortiz, 35, an intel supervisor for the Border Patrol, fled from state troopers and was found hiding in a truck in a hotel parking lot in Laredo at around 2 a.m.