(Bloomberg) -- A former senior official at the Federal Bureau of Investigation pleaded guilty to conspiring to violate US sanctions and launder money while working for Russian billionaire Oleg Deripaska.

Charles McGonigal, 55, had been the special agent in charge of the FBI’s Counterintelligence Division in New York, where he oversaw efforts to root out foreign spies and led investigations of Russian oligarchs, including Deripaska. But after retiring in 2018, McGonigal said he went to work for the billionaire, digging up background on a Deripaska rival, Norilsk Nickel President Vladimir Potanin.

“I never intended to hurt the United States, the FBI or my friends and loved ones,” McGonigal told US District Judge Jennifer H. Rearden in New York on Tuesday, his voice breaking from emotion. His sentencing was scheduled for Dec. 14 and he faces as long as five years in prison.

McGonigal’s plea resolves criminal charges in New York, where he was arrested in January at John F. Kennedy International Airport on his return from an unrelated trip to Asia. He still faces separate charges in a Washington indictment that accuses him of falsification of records and making false statements. 

“He’s accepted responsibility and is trying to move on with his life,” McGonigal’s lawyer, Seth DuCharme, said outside court. DuCharme said his client is “open” to pleading guilty in the Washington case if he can get a fair plea agreement.

As special agent in charge, McGonigal oversaw counterintelligence and national security matters, including an investigation into Deripaska, who had ties to Russian President Vladimir Putin. Deripaska is the majority shareholder of Russian power and metals giant En+ Group International and has a net worth of around $3 billion, according to the Bloomberg Billionaires Index.

McGonigal served in the FBI from 1996 to 2018. He participated in secret investigations of Deripaska and other wealthy and influential Russians, according to the US. Prosecutors said he agreed in 2021 to investigate a Russian rival of Deripaska, in exchange for concealed payments.

In the court hearing, McGonigal told the judge he was paid $17,500 for doing “open-source” research on Potanin, currently the richest person in Russia, according to the Billionaires Index. McGonigal said Deripaska paid the money from an account at the Russian Gazprombank JSC, through a bank in Cyprus, to an account in New Jersey and on to McGonigal. The arrangement was intended to obscure Deripaska as the source of the illegal payments, he said. McGonigal has agreed to forfeit the $17,500.

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Assistant US Attorney Rebecca Dell told the judge that, if the case were to go forward, prosecutors would prove that McGonigal and an unidentified co-conspirator planned to share files that were found on the dark web relating to Potanin for a fee of $625,000 to $3 million.

Special Counsel Robert Mueller’s investigation into Russian election interference explored connections between Paul Manafort, Donald Trump’s one-time campaign chairman, and Deripaska. The Russian businessman is himself separately charged with violating US sanctions, in an alleged scheme to ensure two children he fathered would be born in the US and hold US citizenship. Deripaska hasn’t appeared to enter a plea in the case.

Also charged with McGonigal in the New York case is Sergey Shestakov, a US citizen and a former Russian diplomat, who worked in New York as a court translator. The government claims he lied to FBI agents in a November 2021 meeting in a Manhattan restaurant. Shestakov has pleaded not guilty.

McGonigal retired in 2018, then worked the next year, along with Shestakov, in an unsuccessful attempt to get the sanctions against Deripaska lifted, according to the government. In emails, he and Shestakov referred to Deripaska as “the individual,” “our friend from Vienna” and “the Vienna client,” prosecutors claimed. 

In the Washington case, McGonigal is charged with taking $225,000 in cash from a New Jersey businessman while still working as head of counterintelligence in New York. The New Jersey man had worked for Albanian intelligence decades ago. 

McGonigal traveled outside the US with the man, who allegedly introduced McGonigal to the prime minister of Albania and to a Kosovar politician, the government alleged. McGonigal failed to file the required reports detailing his foreign travel and contract with foreign citizens, prosecutors said.

According to the government, the New Jersey man handed McGonigal $80,000 in cash while seated in a car outside a Manhattan restaurant in October 2017. He gave the then-FBI official cash twice more that year, prosecutors said.

The case is US v. McGonigal, 23-cr-00016, US District Court, Southern District of New York (Manhattan). 

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