DOVER, Del. – The body of a military expert who served in three Republican administrations was found dumped in a landfill over the holiday weekend, and investigators said Monday they do not know who might have killed him. John Wheeler III, 66, was last seen Dec. 28 on an Amtrak train from Washington to Wilmington. His body was found three days later, on New Year's Eve, as a garbage truck emptied its contents at the Cherry Island landfill. His death has been ruled a homicide.