It’s exactly the circumstance Donald Trump tried to avoid. But Trump’s own actions have made an FBI investigation into the president himself a reality.

Firing James Comey, the FBI director, was, by Trump’s explanation, a way to stop a “witch hunt” against his team’s alleged ties to Russia. It led, within weeks, to the appointment of a special prosecutor, Comey’s FBI predecessor, Robert Mueller. And now Mueller is investigating Trump himself for possible obstruction of justice—by firing Comey, who had led the FBI inquiry.

With the crisis engulfing Trump’s young presidency intensifying, senators, Trump aides, former prosecutors, and FBI veterans are sending the White House an urgent warning: Whatever you do, don’t. Fire. Mueller.

News of the obstruction investigation, which was first reported by The Washington Post on Wednesday, comes just days after Trump himself began floating the possibility of firing the new head of the investigation: Robert Mueller, the Justice Department special counsel appointed in the wake of Comey’s firing.

The obstruction investigation has raised the stakes for Mueller’s potential ouster. Firing him now, which would require that Trump personally direct DOJ leadership to do so, would create a political firestorm.

“Firing Robert Mueller right now would be a direct attack on the rule of law by Donald Trump,” Ron Wyden, an Oregon Democrat on the Senate Intelligence Committee, told The Daily Beast. Wyden declined to directly address the Post report.

Trump reportedly floated the possibility of firing Mueller as a way to prod him toward exonerating the president and other Trump associates party to the investigation. The New York Times reported on Tuesday that aides dissuaded him from doing so.

For Ali Soufan, a retired FBI counterterrorism agent, word that Trump is now a target of Mueller’s inquiry explains the trial balloon.

“No wonder President Trump and his surrogates are getting nervous. This explains their sudden attacks on Mueller and the threats to fire him,” Soufan told The Daily Beast.

White House officials are still insisting to the president that he should leave Mueller in his post. “We are all advising him not to [get rid of] Mueller. That has not changed,” one Trump aide told The Daily Beast. “It would be an absolute nuclear explosion if he did.”

Firing Mueller would also put the president in greater legal jeopardy than he already may be in, said former United States attorney Barbara McQuade.

“If Trump were to fire Mueller and it could be shown that his purpose was to impede the investigation, it could be additional evidence of obstruction of justice,” McQuade, who was appointed by President Obama, told The Daily Beast.

“Dear God, Keep Him Away from Twitter”

But some privately concede that Trump is so unpredictable—and so frustrated with the persistence of the investigation and its cost in political capital—that they’re not ruling it out. Another White House official conceded that it would be “suicide” if Trump sacked Mueller at this point, but “I’d be insincere if I said it wasn’t a concern that the president would try to do it anyway.”

For now, officials are simply concerned with limiting fallout from what is sure to be a thunderous reaction from the president to news that he is personally the target of the FBI’s probe.

Asked what the internal game plan should be, one senior Trump administration official replied, “Keep him away from Twitter, dear God, keep him away from Twitter.”

“The president did this to himself,” the official added.

That sentiment reflects a general internal frustration with Trump’s tendency to shoot from the hip in tweets and public statements that are rarely vetted by his legal team and often undercut White House messaging on major issues.

A second senior administration official pointed to Trump’s role in propagating the rumor that he might fire Mueller—according to the Times, he felt the prospect of being sacked might convince Mueller to resolve the investigation in Trump’s favor—and suggested that the leak to the Post on Wednesday might have been an unintended consequence of that move.

“Whoever leaked [news of the obstruction investigation] was obviously reading that he was thinking about giving Mueller the boot,” the official said. Trump “shot himself in the foot again with this cockamamie scheme to get Mueller to play ball.”

“Saturday Night Massacre,” Part Two

Already, legal scholars have been gaming out the implications of Trump sacking Mueller.

McQuade is one of several former Justice Department and White House officials who warned such a firing would likely trigger a cascade of resignations within the Justice Department. “We could then have a repeat of the Saturday Night Massacre or the Sally Yates Massacre,” she said.

The FBI’s obstruction investigation is expected to include interviews with Director of National Intelligence Dan Coates and Adm. Mike Rogers, the head of the National Security Agency, both of whom declined to answer questions about the probe—and reports that Trump tried to enlist them in his campaign to oust Comey—during congressional testimony last week.

A DNI spokesperson declined to comment, and a spokesperson for the National Security Agency said in a statement, “NSA will fully cooperate with the special counsel. We are not in a position to comment further.”

The White House referred questions to Trump’s private counsel, Marc Kasowitz, whose spokesman told the Post, “The FBI leak of information regarding the President is outrageous, inexcusable and illegal.”

The leaks also could give ammunition to Mueller’s critics. Retired Sen. John Danforth, the only other person to act as a special counsel under the same authority as Mueller, told The Daily Beast in May that preventing leaks was a top priority when he investigated the Waco raid. He said everyone who worked on his probe signed a pledge not to leak, and when one person did, that person was fired.

“You can’t have an investigation that is dribbled out there in bits and pieces and suspicions and all of that,” he told The Daily Beast, adding he didn’t want to specifically criticize Mueller’s investigation since he doesn’t know the source of the leaks.

“No leaks,” he added. “It is really important to an investigation. It’s the only fair way to do it. It’s not like a sports game where the score changes every inning, every minute. You’re trying to get a total, complete picture of the facts after you gather all the facts, and not give a play-by-play. It’s really unfair to give a play-by-play, and it’s misleading.”

Ed Dowd, Danforth’s deputy on the Waco investigation and a former U.S. attorney, told The Daily Beast leaks about investigations can generate distrust among investigators.

“When you’re doing an investigation like this, leaks are so destructive to the people under investigation and the morale of the investigators,” he said. “Once you start having leaks, it’s hard to trust the people that are investigating, your fellow investigators. So I think that’s really , really important and I’m sure Bob Mueller feels the same way.

“Obviously you can’t control what other people outside your investigation are going to say and do,” he added.

—with additional reporting by Betsy Woodruff, Justin Miller, and Kim Dozier