The former British spy who allegedly created an incriminating but now-discredited dossier on President-elect Donald Trump reportedly helped the FBI build its case against FIFA officials back in 2010, The Washington Post reported.

Christopher David Steele, 52, was last seen leaving his home in the southwest of London on Wednesday, apparently to avoid detection and escape possible retribution once his identity as the source of the salacious document became known, the New York Times reported.

A person close to Steele said he left his home because he now fears a prompt and potentially dangerous backlash from Moscow against him and his family, the Telegraph reported.

Trump lashed out at the media for publishing the unsubstantiated material and at the U.S. intelligence officials, accusing them of leaking the allegations and likening the leaks to Nazi conduct.

Reuters reported on Thursday that in 2009, Steele’s London-based consulting firm, Orbis Business Intelligence, was hired by England’s Football Association to investigate FIFA over corruption allegations.

It was his work on corruption in international soccer “that lent credence to his reporting on Trump’s entanglements in Russia,” the report said.

Before developing the material on Trump, Steele was hired to investigate former European Commission Vice President Kristalina Georgieva, EurActiv.com said. Steele’s work occurred while Georgieva was a candidate for U.N. secretary-general.

Steele, who previously worked years undercover in Russia, London and France for MI-6, was specifically tasked with investigating her alleged links to a Bulgarian organized crime group known as Multigroup, a shady business empire run by Iliya Pavlov who was assassinated in Sofia in 2003.

Last October Georgieva resigned from the European Commission to take a job with the World Bank.