President Donald Trump s former personal attorney Michael Cohen pleaded guilty Thursday morning in special counsel Robert Mueller s investigation for lying to Congress during private testimony last year about the timing and extent of his discussions about a Russian real estate deal during Trumps campaign.

Cohens cooperation with Muellers investigation marks an extraordinary development, as he has long been a key figure, given his role in Trumps businesses and as his fixer.

According to court documents, Muellers team has focused on Cohens role in Trumps business dealings, particularly a Trump Tower project in Moscow during the 2016 campaign. Cohen lied about the timing of his discussions with Russian officials about the potential real estate deal. Last year, he told the House intelligence committee that the talks ended in January 2016, before the presidential primaries. But, according to court documents, he continued talks as late as approximately June 2016, before Trump became the GOP nominee, discussing the deal several times with Trump and briefing Trumps family members.

Cohen also lied about whether he and Trump, referred to as Individual 1 in Thursdays documents, discussed planning a trip to Russia during the campaign.

COHEN asked Individual 1 about the possibility of Individual 1 traveling to Russia in connection with the Moscow Project, and asked a senior campaign official about potential business travel to Russia, the documents said.

Cohen did not comment while leaving court Thursday morning. His attorney told reporters, Mr. Cohen has cooperated. Mr. Cohen will continue to cooperate.

Asked about Cohens plea deal Thursday, Trump told reporters that Cohen is a weak person and claimed he was lying.