The body of a military expert who served in three Republican administrations was found dumped in a landfill over the New Year's weekend, and investigators said Monday they do not know who might have killed him.

Authorities say John Wheeler III, 66, was scheduled to be on an Amtrak train from Washington to Wilmington on 28 December. Police say it's now not clear if he ever made that trip. 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.

Wheeler, who served as an Army staff officer in Vietnam, later worked in the Reagan and both Bush administrations and helped lead efforts to build the Vietnam Veterans Memorial wall in Washington. He also was the second chairman and chief executive officer of Mothers Against Drunk Driving.

His body was discovered on 31 December as a waste management truck emptied its contents at the Wilmington-area landfill. His death has been ruled a homicide.

Police have determined that all the stops made by the garbage truck on Friday before it arrived at the landfill involved commercial disposal bins in Newark, several miles from Wheeler's home in the historic district of New Castle.

Newark, Delaware police spokesman Lt. Mark Farrall said investigators had been to Wheelers' house, which was roped off with police tape after his death, but that it could not be considered a crime scene.

"We don't have a crime scene at this point in time," said Farrall, adding that investigators still do not have any leads in the case.

Farrall said initial police reports that Wheeler was last seen getting off an Amtrak train in Wilmington last Tuesday were incorrect.

"The information that we have is that he was scheduled to take a train from Washington DC, to Newark on the 28th. We don't know if that occurred," Farrall said, adding that investigators don't know how long Wheeler might have been missing before his body was found, or where and when he was last seen.

Asked why Wheeler had not been reported missing, Farrall said the family was not in town at the time.

"That's why there was some delay in notification," he explained.

A graduate of the US Military Academy at West Point, Wheeler went on to study at Harvard Business School and Yale Law School.

Richard Radez, a longtime friend who also graduated from West Point and Harvard Business, said he exchanged e-mails with Wheeler on Christmas. On the day after Christmas, Wheeler sent Radez an e-mail expressing concern that the nation wasn't sufficiently prepared for cyber warfare.

"This was something that had preoccupied him over the last couple of years," Radez said.

James Fallows, a national correspondent for The Atlantic magazine, wrote in an article on the magazine's website that he had known "Jack" Wheeler since the early 1980s.

Wheeler, Fallows wrote, had spent much of his life trying to address "what he called the '40 year open wound' of Vietnam-era soldiers being spurned by the society that sent them to war."

Wheeler retired from the military in 1971, and went on to serve in the administrations of Presidents Ronald Reagan and George H.W. Bush, including at the Securities and Exchange Commission. He also was a special assistant to the Secretary of the Air Force under President George W. Bush. He recently worked as a consultant for The Mitre Corporation, a nonprofit based in Bedford, Mass., and McLean, Virginia, that operates federally funded research and development centers.

"He was just not the sort of person who would wind up in a landfill," said Bayard Marin, an attorney who was representing Wheeler and his wife, Katherine Klyce, in an ongoing legal dispute with a couple wanting to build a home near the Wheelers' in the historic district.

"He was a very aggressive kind of guy, but nevertheless kind of ingratiating, and he had a good sense of humor," Marin said.