A day after Trump’s former national security advisor, Michael Flynn, pleaded guilty and agreed to cooperate with special prosecutor Robert Mueller, who is investigating the Trump team’s alleged ties to the Kremlin, Trump tweeted about Flynn:

“I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide!”

Whether the president remembered it or not, he has never before stated that Flynn lied to the FBI. Whether the president realized it or not, conceding that he knew about Flynn’s FBI lie – to which Flynn pleaded guilty on Friday – opens Trump up to a world of legal hurt. Trump had asked James Comey, the former director of the FBI, to drop an inquiry into a man Trump now says he knew lied to the bureau.

“This tweet makes it clear that Trump knew at the time that he made his request to Comey to let the investigation go that Flynn had lied to the FBI, which is a criminal offense,” Barbara McQuade, who until January served as the U.S. attorney for the Eastern District of Michigan, told The Daily Beast.

Trump’s original explanation for firing Flynn on the evening of February 13 was that Flynn had lied to Vice President Mike Pence about his December conversations with then-Russian ambassador Sergey Kislyak concerning new U.S. sanctions on Russia. On February 14, then-White House press secretary Sean Spicer said Trump fired Flynn for what Spicer called an “evolving and eroding level of trust” with Flynn.

That same day, Trump met with several national security officials, including Comey, and dismissed the others to talk with Comey in private. Comey at the time was in charge of the Russia inquiry.

“I want to talk about Mike Flynn,” Trump told him, according to Comey’s sworn Senate testimony in June. “The President began by saying Flynn hadn’t done anything wrong in speaking with the Russians, but he had to let him go because he had misled the Vice President.” (If Trump told Comey that Flynn lied to the FBI, Comey did not include that in his highly anticipated testimony.)

Trump quickly got to the point of the one-on-one discussion.

“I hope you can see your way clear to letting this go, to letting Flynn go,” Comey quoted Trump saying. “He is a good guy. I hope you can let this go.”

Comey said he promised Trump nothing, and considered Trump’s request such a breach of FBI independence from the White House that he prepared a memo on it – a subpoenable document, in other words – that he shared with his FBI leadership team and not Attorney General Jeff Sessions.

Less than three months after that meeting, Trump fired Comey, citing the Russia investigation as the cause to NBC’s Lester Holt, which itself was a revision from the initial White House excuse that Comey had mistreated Hillary Clinton.

Trump’s tweet “adds to the evidence that Trump was attempting to obstruct or impede the investigation of a crime,” said McQuade, the former federal prosecutor.

The admission from the president also suggests that White House counsel Don McGahn had informed the president about Flynn’s potential to “be blackmailed by the Russians,” as Sally Yates, the former acting attorney general, put it in May testimony.

Yet according to the timeline Yates provided of briefing McGahn, Trump kept in office for another 18 days a man he now says he knew lied to the FBI – deepening Flynn’s compromise, and even potentially Trump’s, should the Russians have come to know Trump was sticking with Flynn.

“ Trump had asked James Comey, the former director of the FBI, to drop an inquiry into a man Trump now says he knew lied to the bureau. ”

Flynn lied to the FBI in an interview on January 24. Yates testified that on the morning of January 26, she called McGahn with “a very sensitive matter” she needed to discuss with the White House counsel in person. That day and the next, Yates told McGahn that Flynn was in a “compromise situation” owing to Pence’s untrue public presentation of Flynn’s conversations with Russian ambassador Kislyak.

In her public testimony, Yates was careful not to discuss two pieces of classified information. First, U.S. intelligence had intercepted the Flynn-Kislyak conversations – legally, since Kislyak was an agent of a foreign power; as the other party on the call, Flynn was collected “incidentally,” in surveillance parlance – thereby disproving Pence’s public account of the calls. Second, Flynn had just given the FBI what Flynn has now conceded was an untruthful account of the Kislyak conversation.

But without saying Flynn had lied to the FBI, Yates made it nonetheless clear that Flynn’s FBI interview was significant enough to prompt her urgent White House visit. (After all, Pence’s TV appearance was on January 15, 11 days prior.) Yates said she had “notes that described that interview” that she took to her parley with McGahn, along with a senior Justice Department national-security official in contact with the FBI. As well, Yates recalled that during a follow-up meeting on January 27, McGahn asked her about “the applicability of certain statutes, certain criminal statutes” to Flynn.

Yates said she was not in a position to know what McGahn did with the “urgent” information on Flynn that she gave to him. She did not hear from the White House counsel again until January 30, she testified: “I don't know what happened after that because that was my last day with DOJ” – when Trump fired her, ostensibly for her refusal to defend Trump’s anti-Muslim travel ban in court. Mueller interviewed McGahn last week, the Washington Post confirmed.

Flynn’s agreement to cooperate has substantially deepened the White House’s exposure to Mueller’s probe. There are not many administration officials senior to Flynn against whom Mueller would want him to testify. While Mueller has never confirmed that Trump himself is under investigation, Trump is on that short list.

Also there are Trump’s son-in-law and Pence himself, all of whom were senior transition-team officials at the time of the Kislyak calls. Pence, who has evaded suspicion in the Russia probe until now, ran the transition. Flynn’s agreed stipulation of the facts of the Kislyak calls claims they occurred with the full knowledge, and in one case at the direction, of the transition team.

As well, Flynn’s decision to seek a plea caused Trump to privately seethe weeks in advance, The Daily Beast reported Friday. Long before Flynn ever says Trump’s name on a witness stand, the plea deal appears to have prompted Trump to casually and publicly proffer information that could lead Mueller to his doorstep.