Isikoff claims that the conspiracy theory, that Seth Rich, a DNC staffer, was killed because he stole the DNC emails which Wikileaks later published, was planted by Russia's foreign intelligence service.

Exclusive: The true origins of the Seth Rich conspiracy theory.

WASHINGTON — In the summer of 2016, Russian intelligence agents secretly planted a fake report claiming that Democratic National Committee staffer Seth Rich was gunned down by a squad of assassins working for Hillary Clinton, giving rise to a notorious conspiracy theory that captivated conservative activists and was later promoted from inside President Trump's White House, a Yahoo News investigation has found.

Russia's foreign intelligence service, known as the SVR, first circulated a phony "bulletin" — disguised to read as a real intelligence report —about the alleged murder of the former DNC staffer on July 13, 2016, according to the U.S. federal prosecutor who was in charge of the Rich case. That was just three days after Rich, 27, was killed in what police believed was a botched robbery while walking home to his group house in the Bloomingdale neighborhood of Washington, D.C., about 30 blocks north of the Capitol.