By Steve Neavling
Special counsel Robert Mueller’s team investigating Russian interference in the 2016 presidential election has lost one of its top FBI investigators.
Sources told ABC News that FBI veteran Peter Strzok stepped down for unknown reasons, marking the first known hitch in the investigation.
Strzok, who is a counterintelligence expert, is now working for the FBI’s human resources division.
He is no stranger to complex and controversial investigations.
As chief of the FBI’s counterespionage section last year, he helped oversee the FBI’s investigation into Hillary Clinton’s use of a private email server, and he took part in the FBI interview of the Democratic presidential candidate.
Within weeks of the Clinton probe ending, Strzok found his office facing a new challenge: investigating Russia’s alleged efforts to influence last year’s presidential election, including a cyberattack on the Democratic National Committee.
A spokesman for the special counsel’s office declined to comment.