Samuel Patten, the Republican operative who pleaded guilty on Friday to failing to register as a foreign lobbyist, was not charged with the offense by special counsel Robert Mueller’s office, yet his case is tied to the broader web covered by Mueller’s expansive investigation.

Patten worked in Ukraine around the same time as Manafort and worked with Manafort associate Konstantin Kilimnik. His case was referred by Mueller and is being handled by the U.S. attorney in Washington and the Justice Department’s National Security Division. Two members of Mueller’s team, FBI special agent Omer Meisel and prosecutor Andrew Weissman were spotted in the courtroom for Patten’s hearing on Friday.

The charging document filed Friday accuses Patten of acting as a foreign agent for the Opposition Bloc, a Ukrainian political party, between 2014 and 2018 without registering with the U.S. government. Prosecutors charge in the filing that Patten owned a consulting company with an unnamed Russian national and was paid by a Ukrainian oligarch through a Cypriot account.

As part of his work for the Opposition Bloc, Patten was in contact with members of Congress, the executive branch, and members of the American media, according to the charging document. He also allegedly arranged for the unnamed Russian national and unnamed Ukrainian oligarch to meet with members of Congress and their staff, per the filing. Specifically, he set up meetings in January 2015 between the Ukrainian oligarch and members of the congressional foreign relations committees, staffers at the State Department and American journalists, according to prosecutors.

Patten helped the Ukrainian oligarch write an op-ed in January 2017 and was successful in placing the piece in an American media outlet in February 2017, according to the charging document.

According to the Friday filing, the Ukrainian oligarch directed Patten not to register as a foreign agent while he was working for the Opposition Blog.

Patten worked with Konstantin Kilimnik, a suspected Russian intelligence operative who also worked as a business deputy and translator in Ukraine for Manafort. Patten also worked for the parent company of Cambridge Analytica, the data company that worked for President Trump’s campaign, ahead of the 2014 elections to help develop their voter targeting program, according to The Atlantic.

Patten and Kilimnik first worked together at the International Republican Institute, a non-profit funded by the U.S. government that promotes Western-style democracy and is tied to the GOP. Kilinmnik worked under Patten as a translator between 2001 and 2004, according to The Washington Post.

The two then formed Begemot Ventures International together in February 2015, as The Daily Beast reported back in April. Patten acknowledged his partnership with Kilimnik to the Daily Beast and said that the company was a political consulting firm that operated abroad.

He consulted for Kiev Mayor Vitali Klitschko’s re-election campaign in 2015, according to The Atlantic. Patten acknowledges his work in Ukraine on his website, but he does not go into much detail.

“Sam has worked for multiple political parties and office-holders in Ukraine, exceeding expectations in each instance,” the website reads.

Patten told The Atlantic in April that he was still in touch with Kilimnik at the time, even as Manafort faced charges stemming from his work in Ukraine with Kilimnik.

“As you might imagine, the barrage of shade and innuendo that has been cast on him since Manafort had his time in Trump Tower has not been something he’d welcomed, nor anything that could objectively be called fair,” he told The Atlantic.

Based on the previous reporting on Patten, it appears that the unnamed Russian national, referred to as “Foreign National A” in the charging document, is Konstantin Kilimnik. The “Company A” referenced in the charging document fits the description of Begemot Ventures International, the firm started by Patten and Kilimnik.

The identity of the unnamed Ukrainian oligarch, referred to as “Foreigner B” in the filing, is a little less clear, but there’s one leading theory right now. Politico’s Josh Gerstein found an op-ed penned by Serhiy Lyovochkin in February 2017, which lines up with the dates in Friday’s filings.

Lyovochkin formerly worked for ex-Ukrainian President Victor Yanukovych and is now a member of the Ukrainian parliament and a top official in the Opposition Bloc, the Ukrainian political party for which Patten did consulting work. Yanukovych was Manafort’s main client when he worked in Ukraine, and Lyovochkin was also one of Manafort’s financiers, special counsel Robert Mueller’s team alleged in Manafort’s Virginia trial.

Read the filing below:

Tierney Sneed contributed reporting.