But no one did more to advance the theory — for which there's no evidence — than Fox's Sean Hannity, who devoted multiple segments on his show to the issue as it took off on conservative blogs and talk radio. Rich's brother wrote a letter to Hannity's executive producer this week asking him to stop.
On Tuesday, Fox retracted the story.
"On May 16, a story was posted on the Fox News website on the investigation into the 2016 murder of DNC Staffer Seth Rich. The article was not initially subjected to the high degree of editorial scrutiny we require for all our reporting. Upon appropriate review, the article was found not to meet those standards and has since been removed," Fox News said in a statement posted online.
The statement did not include an apology to Rich's family or any admission of regret.
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Rich's family had specially demanded an apology. But a spokesperson for Rich's family reacted to the Fox retraction by suggesting the family wanted to put the episode behind them and move on.
"The family would like to thank Fox News for their retraction on a story that has caused deep pain and anguish to the family and has done harm to Seth Rich's legacy," family spokesman Brad Bauman said in a statement. "We are hopeful that in the future that Fox News will work with the family to ensure the highest degree of professionality and scrutiny is followed so that only accurate facts are reported surrounding this case."
Long before the retraction, the Fox News story fell apart factually almost the moment it was published.
Within a day, one of its main sources — a private investigator working with Rich's family, but paid for by a conservative Dallas millionaire — recanted his story. The family has since sent him a cease and desist letter.
Subsequent reporting by NBC News and other outlets also found that the local police investigating Rich's death never even gave his laptop to the FBI, so there was no way Fox's purported source could have seen it.
A former law enforcement official with first-hand knowledge of Rich's laptop told NBC News definitively: "It never contained any e-mails related to WikiLeaks, and the FBI never had it."
The Daily Caller, a conservative news outlet, apparently removed their story based on the Fox News report with any retraction or editor's note explaining its disappearance from the Internet.
Hannity, however, showed no signs of backing down.
On his radio show Tuesday, he pressed on with the Rich case, even after his employer's retraction, and lashed out at critics. "For those accusing me of pushing a conspiracy theory, you are the biggest phony hypocrites in the entire world," he said.
Rich was shot and killed at age 27 while walking home late one night last July in what police suspect was a robbery gone wrong. The case is still unsolved.