A mysterious professor who made a major appearance in court filings related to Special Counsel Robert Mueller’s plea agreement with former Trump campaign advisor George Papadopolous was in Russia just a few weeks before the court documents were unsealed, Buzzfeed reported Tuesday.

Joseph Mifsud participated in a Oct. 5, 2017 seminar in Moscow — timed to Saudi Arabia’s King Salman bin Abdulaziz Al Saud visit to the country — about Yemen security issues, according to Buzzfeed’s report. The report cites a visa dated Oct. 4, 2017, as well as two sources at the Russian Council of International Affairs, the think tanks that organized the seminar. The sources told Buzzfeed that Mifsud was a member of the Saudi king’s delegation.

On Oct. 30, Mueller unsealed court documents related to Papadopoulos’ plea deal that referenced communications Papadopoulos had with a professor who, among other things, told Papadopoulos that the Russians had dirt on Hillary Clinton. Papadopoulos pleaded guilty to lying to FBI agents about those communications.

Mifsud, a Maltese citizen based in London, confirmed soon after the docs were unsealed that he was the professor in question. His whereabouts have been unknown since he was interviewed by an Italian news outlet in Rome on Oct. 31.