The Washington Post reports in its Saturday editions that many of the stab wounds were shallow puncture wounds described as "prick marks" on his chest, neck and head, suggesting he had been tortured.
Investigators are interviewing people connected with cases Luna prosecuted, as well as friends and associates, but no immediate promising leads have come up, said a federal law enforcement official, speaking to The Associated Press on condition of anonymity.
Luna, who officials said was stabbed 36 times, was dressed in a suit and overcoat, and had his wallet with identification and cash, but it was unclear whether he had been robbed, Lancaster County, Pa., coroner Dr. Barry Walp said Friday.
Money and cell phone equipment also were found inside his car, which had blood on the driver's side door and fender and a large pool of blood on the floor, according to a police search warrant application. A police affidavit said Luna also had a "traumatic wound" on the right side of his head.
Luna also sustained several serious stab wounds, each at least four inches deep, the Post quotes Walp as saying.
Walp told the Post Luna was still breathing when he was dumped facedown in the frigid water. He said he believes Luna died from a combination of the stab wounds and drowning.
"He was alive when he was put in the creek," Walp said to the Post, adding that creek water was found in Luna's lungs. Referring to the numerous "prick marks," Walp said, "You would think they were perhaps after information from the guy when you see something like this, or perhaps for kicks."
A Pennsylvania district attorney said Saturday that authorities are looking "at every possibility" as they try to determine what led to the gruesome killing of a federal prosecutor who was stabbed 36 times and found face down in a creek.
Lancaster County District Attorney Donald R. Totaro wouldn't comment on whether investigators had specific theories or suspects in mind, but he denied media reports that investigators had determined the attack on Johathan Luna was the result of a personal dispute.
"There are many avenues that need to be explored, so I think it would be very premature to suggest that this case or the course of this investigation has been narrowed to that extent," Totaro said.
He said he spoke Saturday with Thomas DiBiagio, the U.S. attorney in Maryland who had been Luna's boss, and said they planned to meet Monday to discuss strategy in the joint investigation, which also includes the FBI and Pennsylvania State Police.
Luna apparently was attacked after leaving his office in Baltimore around midnight Wednesday, the federal law enforcement official told the AP.
The FBI worked to create a timeline of what Luna did in his last hours.
By 5 p.m. Wednesday, Luna and defense attorneys had reached a plea bargain in the case of rap musician Deon L. Smith and Walter O. Poindexter, who were on trial on charges of running a violent heroin ring from their studio, according to the judge presiding over the case.
Poindexter's attorney, Arcangelo Tuminelli, said he got a call from Luna at 9:06 p.m. in which the prosecutor said he was still drawing up the paperwork for the plea and making sure it was all correct.
Tuminelli said he did not where Luna was at that point. But he said Luna told him he had to go home and would be back in his office in the federal courthouse in Baltimore later.
"I assumed there would be a fax at my house of the agreement by about midnight," Tuminelli said. The fax never came.
One federal law enforcement official said authorities had determined Luna left his home early in the evening and went back to his office to work on papers in the plea bargain. He was there until around midnight, the source said.
Another source who spoke on condition of anonymity said there were personal items in Luna's office that one "would have expected him to be taking home had he been leaving to go home for the evening." The source declined to describe the items.
Authorities have not said whether the rapper's case had anything to do with the slaying. Smith and Poindexter were behind bars at the time.
Smith's attorney, Kenneth Ravenell, says it would make no sense for his client or Poindexter to be involved.
"The deal that Mr. Smith pled guilty to was a deal we offered to the prosecutors two weeks before the trial," he told CBS News Early Show co-anchor Hannah Storm. "Mr. Luna was instrumental in negotiating that deal and convincing his office that it was a proper deal. So both men had the deal that they had sought from the prosecution."
Tuminelli said the FBI interviewed Poindexter on Thursday night.
"He had absolutely no information that would be of help to them," he said. "I believe that this has nothing to do with my client or Mr. Smith."
Tuminelli said Smith also consented to be interviewed by authorities.
The last federal prosecutor to be slain was Assistant U.S. Attorney Thomas C. Wales, who was shot to death in Seattle in October 2001.
"We feel horrible for Mr. Luna and his family and the whole Baltimore U.S. Attorney's Office," said Mark Bartlett, an assistant U.S. attorney in Seattle. "Just reading about the case reminds us that Tom's case has not been solved, and that's a continuing source of sadness and frustration."