Three months after American David Hartley was shot and killed by a drug gang while jet-skiing with his wife on a lake straddling the Texas-Mexican border, U.S. investigators say the gunmen were "authorized" by their cartel to kill Hartley's wife, as well. David Hartley...was shot in the back of his head on Sept. 30 by alleged Mexican drug smugglers while jet-skiing on Lake Falcon with his wife, Tiffany. Tiffany Hartley...said her husband was shot when the two tried to dodge bullets from three speed boats driven by the alleged smugglers. Hartley's body has never been recovered. Mexican authorities in October...