Police in Newark, Del., have recovered John Wheeler's cell phone in the house under construction across the street from Wheeler's home in New Castle. Del., reported ABC affiliate WPVI in Philadelphia.
The ex-presidential appointee had filed a lawsuit, challenging the zoning approval for the neighboring house because it partially blocked his view of Battery Park and the Delaware River.
Police have been looking into the possibility that Wheeler may have set off smoke bombs in the house earlier last week.
Wheeler reportedly fought with a neighbor over the construction of the home. An attorney for that neighbor issued a statement saying his client was saddened by Wheeler's death.
Authorities have also interviewed a cab driver after finding his phone number on Wheeler's cell phone.
The driver, Athel Scott, said he doesn't know how his number got on Wheeler's phone, but he said he does remember seeing him.
"I seen him one day by the Hotel duPont and one day I seen him at the train station going inside that little store, that's all I know," Scott said.
Police also announced Friday they have uncovered more surveillance video from the night Wheeler was last seen alive. The video shows Wheeler leaving the Nemours Building in Wilmington, then walking down the street, passing through the Hotel duPont valet parking area further, before crossing over to Market Street.
In one portion of the video, the 66-year-old Wheeler appears confused as he held a shoe in one hand, and limping slightly. He is last seen on camera at 8:42 p.m. on Dec. 30.
Former homicide investigator Brad Garrett told ABC News, "So the, the question for investigators is, does it all really go together or is it pieces? When I say pieces, did he have a stroke, for example? Becomes disoriented, he wanders around. He hits into the wrong crowd. They kill him. They rob him, whatever they might do."
Wheeler's death remains a distressing mystery for his family and the police.
Investigators are continuing their efforts to talk to Wheeler's friends and associates, and are asking for the public's help. Meanwhile, Wheeler's family issued a statement today, thanking the police for their efforts:
"The family of John P. Wheeler III is most grateful for the efforts of the law enforcement authorities in the ongoing investigation into his death. The family is sincerely thankful for all the personal expressions of sympathy and condolences received from so many whose lives were touched by Jack in such positive ways. We reiterate our previous requests for privacy as we mourn his loss and ask that our decision to refrain from further comment at this time be respected."
Wheeler, a former presidential appointee and defense consultant, was found dead as his body was being dumped out of a dumpster into a Wilmington, Del. landfill on New Year's Eve.
Mystery Deepens in Wheeler Death
Police said they still don't know some basic facts in the case, like where and when Wheeler was killed. They are investigating the case as a homicide.
Police traced the route of the garbage truck that dumped Wheeler's body, and discovered the truck's pickup route was in nearby Newark.
This sparked questions about the timeline of Wheeler's death. If Wheeler was killed in Wilmington, the killer or killers would have had to transport his body to Newark to place it in the dumpster. If he was killed in Newark, police wonder how he got there when he seemed disoriented, and told a parking garage attendant he was having trouble finding his car.
Wheeler's mysterious movements and his work as a Washington insider has sparked speculation that he may have been targeted in some kind of conspiracy. But Garrett said he has his doubts.
"It may not be as nefarious. This may not be a spy novel. It just may be a murder," he said.
Wheeler was an Army officer during the Vietnam War. He served in the administrations of three Republican presidents: Ronald Reagan, George H.W. Bush and George W. Bush, for whom he was a special assistant to the Secretary of the Air Force.
Wheeler was a West Point graduate and helped spearhead the funding drive to get the Vietnam War Memorial in Washington, D.C. built. He moved easily among Washington's elite, working most recently as a military consultant.
Questions About Wheeler Timeline
Police said Monday they don't know where he was killed, why he was killed, or who may have killed him.
Investigators continue to scour the landfill for leads.
"We have no suspects at this time," Farrall told ABC News. "What's important now is to establish the location of the crime."
Farrall said that Wheeler, who had homes in Washington, D.C., and in New Castle, was scheduled to take a train from Washington to Wilmington, Del., on Dec. 28.
But at this point, Farrall said, police have no information about Wheeler's whereabouts that week.
"His family was travelling, so no one reported him missing," Farrall said.
Wheeler's death has saddened many of his close friends, including former CIA Director James Woolsey and author James Fallows.
Fallows wrote a tribute to Wheeler in the Atlantic Magazine online, saying, "I feel terrible for his family and hope they will eventually find comfort in knowing how many important things he achieved."