Boston (CNN) -- A man who'd been prepared to testify in the trial of reputed Boston mob boss James "Whitey" Bulger was found dead -- a day after, a friend says, he learned he was dropped from the prosecution's witness list.
Massachusetts State Police are investigating the death of Stephen Rakes, 59, the Middlesex County district attorney's office said Thursday.
A jogger reported finding Rakes' body Wednesday in Lincoln, west of Boston, said Stephanie Guyotte, a spokeswoman for the district attorney's office.
An autopsy to determine cause and manner of death was conducted Thursday by the chief medical examiner's office and no signs of trauma were found, according to Guyotte. Results are pending toxicology tests, which generally takes several weeks to complete.
Bulger is charged in the deaths of 19 people during some two decades when prosecutors say he terrorized South Boston as the head of the Irish mob. He also faces charges of extortion, racketeering and money laundering. He has pleaded not guilty to all charges.
Rakes had alleged that Bulger forced Rakes to sell his South Boston liquor store to him in the 1980s.
Steve Davis, a brother of one of Bulger's alleged murder victims and a friend of Rakes, said that Rakes learned Tuesday that the prosecution had dropped him from its list of potential witnesses.
"I was upset for him ... because he was looking forward to" testifying, said Davis, who said he'd become close to Rakes in the months leading to Bulger's trial, which began in June.
Davis said he tried to reach Rakes on Tuesday but his call was not returned.
Asked whether Rakes was upset about being dropped, Davis said: "I think it was real devastating to him."
Last Monday, former Bulger associate Kevin Weeks testified that "it wasn't your regular extortion," adding that Rakes offered to sell his store to Bulger.
Weeks explained to the federal jury that Rakes was willing to sell his liquor store Stippo's for $100,000, but tried to back out of the deal at the last second.
Weeks, who on the stand repeated over and over "I don't like Rakes," said that Bulger had forced the store owner to take the deal.
Rakes later told the media that Weeks was a liar and that his liquor store was "never for sale."
Weeks turned state's evidence after he found out Bulger was an FBI informant and led law enforcement to a quarry of shallow graves in Boston tidal marshes. He pleaded guilty to assisting in five murders in 2000 and served five years in prison in exchange for cooperating against Bulger.
A representative of the U.S. attorney's office that is prosecuting Bulger declined to comment Thursday on the death.
Rakes "showed up at court every day for this trial," Boston Globe columnist Kevin Cullen told "CNN Newsroom." He said he last saw Rakes at the trial on Tuesday.
"He's been waiting decades to tell his story," Cullen said.
Michael Connolly, a lawyer who once represented Rakes, told CNN on Thursday that he was shocked to learn of Rakes' death.
"I saw him a month ago, and he looked fit, healthy, and was in good spirits," Connolly said. "He was looking forward to testifying at the 'Whitey' Bulger trial."
CNN's Susan Candiotti and Ross Levitt contributed to this report.