The convoluted case of the murder in Washington, D.C., of Democratic operative Seth Rich has taken another turn, with a lobbyist who has been investigating the case claiming a "credible" witness has been found.

Jack Burkman, a Washington-based lawyer and lobbyist, told the Gateway Pundit blog: "We believe that we have reached the beginning of the end of the Seth Rich murder investigation. After two long hard years of work, we have a witness who is prepared to identify the two killers of Seth Rich."

Burkman told the blog in an exclusive interview on Sunday that one of the culprits identified by the witness is an agent for the Drug Enforcement Administration and the other is an agent for the ATF, the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Burkman said the witness has conclusive evidence that will bring the killers to justice.

As WND has reported, Rich, 27, the DNC’s voter expansion data director, had accepted a position with Democratic Party nominee Hillary Clinton’s campaign just before his death.

On July 10, 2016, he was fatally shot in the back in Washington, D.C., near his apartment in an affluent neighborhood. Rich had been working for the DNC at a time when emails from the organization were provided to WikiLeaks for publication.

The Metropolitan Police Department and Washington Mayor Muriel Bowers insist Rich was randomly killed during a "botched robbery." But others are doubtful because he was found with his wallet, credit cards and other valuables.

The new Gateway Pundit report said the witness fears for his life, and plans to have armed guards and a disguise to protect him.

Burkman told the blog Frank Whalen, a retired NYPD detective sergeant, found the witness.

"We found him through working with a retired New York City detective, who found him and brought him to us. We have thoroughly vetted this witness and we believe in this witness," Burkman said. "He has evidence that substantiates his claims but it will be revealed slowly. This witness is in great fear of his life – that’s why we are going with disguising him, disguising his voice and everything about him."

WND has reported on the case since its outset, reporting just weeks ago the Department of Justice was refusing to release any records related to the murder, according to a lawyer who has been investigating the unsolved case.

The lawyer, Ty Clevenger, reported on LawFlog he received the news from the Executive Office for U.S. Attorneys.

"Actually, they have refused to release any records about Seth Rich at all, e.g., whether he had a security clearance or a background check."

But he pointed out the "same office originally refused to even search for records related to Seth Rich, but it was overruled on October 2, 2017, after I appealed to DOJ's Office of Information Policy.'

WND is serious about investigating the Seth Rich case through its conclusion. You can help us through our new GoFundMe page today!

WND reported last fall when Clevenger started his hunt for the Rich records.

After his FOIA request for records or correspondence about the murder or its investigation was rejected, the DOJ at that time told the U.S. Attorney's Office for Washington, D.C., to hunt for records.

The U.S. Attorney’s Office originally put off Clevenger's FOIA request, demanding he submit a death certificate to prove that Rich was dead.

"Since you have not furnished a release, death certificate, or public justification for release, the release of records concerning a third party would result in an unwarranted invasion of personal privacy and would be in violation of the Privacy Act, 5 U.S.C.§ 552a," the office said.

But Clevenger appealed. And Sean R. O'Neil, the chief of administrative appeals at DOJ's Office of Information Policy, directed the executive office for U.S. attorneys to search for and produce any records covered in Clevenger's FOIA request.

WikiLeaks founder Julian Assange has hinted that Rich, and not Russian agents, may have been the source of the Democratic National Committee emails he published online.

The case has caused considerable distress for Democrats. WND reported last year when former DNC Chairwoman Donna Brazile appeared incoherent and agitated when WND approached her at a book signing to ask her questions about murdered DNC staffer Seth Rich.

Brazile said in her new book, which is dedicated to Rich, that she was deeply concerned about Rich's mysterious murder and had discussed it in a phone call with Democratic presidential nominee Hillary Clinton after Clinton's election loss.

She wrote that she asked Clinton to contribute to a reward fund to help find the slain DNC staffer's murderer, but Clinton ended the phone call.

The following is an excerpt from Brazile's book "Hacks: The Inside Story of the Break-ins and Breakdowns That Put Donald Trump in the White House":

I knew the campaign had over $3 million set aside in a legal fund. Could she help me get this lawsuit started? And don't forget the murder of Seth Rich, I told her. Did she want to contribute to Seth's reward fund? We still hadn't found the person responsible for the tragic murder of this bright young DNC staffer. You're right, she said. We're going to get to that. But she really had to go. She had made the call and checked it off her list, and I accepted after we said our good-byes that I might never hear from her again.

WND attended Brazile's Dec. 12 book signing at the National Press Club in Washington, D.C., and asked her why she believes Clinton seemed unconcerned about Rich's murder and unwilling to allocate campaign money as a reward to find Rich's killers.

But Brazile contradicted statements in her book, flat-out denying she even made them.

"You say in your book that you urged Hillary Clinton to use campaign funds as reward to find Rich's murderer(s). And Clinton briefly responded by saying she really had to go," WND stated, before Brazile interjected.

"I – I never read – I never wrote that. No," she said.

"We discussed – on Dec. 1 we offered – Jim Roosevelt [co-chair of the DNC rules and bylaws committee] proposed that the DNC raise money to help with the reward fund, and we urged members to provide resources. But at no time did I tell Hillary – in the book, I said, 'Don't forget Seth Rich.' That's what I said in the book," she claimed.

WND also pressed Brazile on why the DNC has offered no reward money to help find Rich's killers.

The former DNC chairwoman and CNN contributor then became visibly angry and accused WND of trying to "smear" Rich and his family for mere "sensationalism."

"Once again, I would like to go on the record as saying that the attempt to smear Seth Rich has caused enormous harm to his family," she charged. "Joel and Mary (Rich's parents) deserve better than that kind of salacious, sensational type of journalism."

At some points, she appeared lost for words and made bizarre and rambling statements: