One by one this winter, then-FBI Director James B. Comey pulled aside three of the bureau’s top officials for private chats. In calm tones, he told each of them about a private Oval Office meeting with President Trump — during which, Comey alleged, the president pressed him to shut down the federal criminal investigation of Trump’s then-national security adviser, Michael Flynn.

Those three officials, according to two people with detailed, firsthand knowledge of the matter, were Jim Rybicki, Comey’s chief of staff and senior counselor; James Baker, the FBI’s general counsel; and Andrew McCabe, then the bureau’s deputy director, and now the acting director, following Trump’s firing of Comey last month. Comey spoke to them within two days of his Oval conversation with Trump, the sources said, and recounted the president’s comments about the Flynn investigation.

The White House and Trump have categorically denied Comey’s account, which Comey reportedly detailed in his own notes shortly after his encounter with Trump. Thus far, the allegation has played as a he-said, she-said between the president and the director he abruptly removed.

That no longer appears to be the case — it will be Trump’s word versus the word of Comey and at least three other leaders of the FBI.

The FBI officials, identified here for the first time, could now emerge as corroborating witnesses for Comey’s story, both in the public debate and in the criminal investigation led by special counsel Robert Mueller. (Other outlets have revealed Comey discussed the encounter with FBI colleagues, but have not identified the officials in question.)

A spokesperson for the FBI declined to comment for this story. The White House did not return calls seeking comment. Two attorneys recently hired by Mueller did not return phone calls either.

On Wednesday, McCabe is scheduled to testify before a Senate committee. It is unclear whether he will testify about his private discussions with Comey. A senior law enforcement official told me that McCabe, Rybicki, and Baker now all consider themselves potential fact witnesses to Mueller’s probe.

Comey himself will testify a day later, before the Senate Intelligence Committee, where he is expected to recount his Oval Office encounter with Trump. It will be the first time Comey has spoken publicly of the matter. CBS, NBC, and ABC will air his testimony live.

For many members of Congress, much of Mueller’s new staff, and the American public, it will be the first time they hear Comey tell a detailed account of Trump pressuring him to shut down the FBI’s investigation of Flynn over his contacts with Russia during and after the 2016 presidential campaign.

Central to the special counsel’s investigation will be whether Trump, in allegedly attempting to interfere with the Russia investigation, acted within the law or crossed the line and engaged in obstruction of justice.

The three officials in question are all lawyers — and, likely, note takers

It is unclear whether each of the officials Comey told of the encounter took notes on their conversations with the director about Trump. But the FBI’s culture is one of creating contemporaneous notes and records, even on matters of far less importance. All three of the FBI officials are also lawyers, a profession known for its record keeping.

Rybicki has had a long career in both the US Department of Justice and FBI. At the Justice Department, he worked for the deputy attorney general, the National Security Division, the Office of Intelligence Policy and Review, and the United States Attorney’s Office for the Eastern District of Virginia, according to his official biography posted on the FBI’s website.

At both Justice and the FBI, he worked on both counterterrorism and counterintelligence matters, meaning that he was certainly read into the FBI’s investigations of whether the Trump campaign or administration officials colluded with Russia to interfere on Trump’s behalf to win a razor-thin election.

Baker, too, has national security experience. From 2001 to 2007, he headed the Justice Department’s office that would later formally become the department’s National Security Division. An FBI press release about Baker’s appointment as FBI general counsel states that while in that position, Baker “developed, coordinated, and implemented national security policy with regard to intelligence and counterintelligence matters for the department.”

The press release went on to note that Baker “provided the attorney general, the U.S. intelligence community, and the White House with legal and policy advice on a range of national security issues and conducted oversight of the intelligence community, including the FBI, on behalf of the attorney general.”

One senior law enforcement official familiar with the matter said that Comey specifically sought legal advice from Baker about when and how to tell the DOJ about Trump pressing Comey to shut down the Russia probe. The same official said that Comey and Baker had more than one discussion about the matter, and that Baker almost certainly made extensive notes about those deliberations.

Both Comey and Baker sought the advice of Rybicki and McCabe as to whether to inform the Justice Department of Trump’s pressure of Comey to shut down the Russia probe, according to this same official. All four of them had reservations about doing so because they did not fully trust Attorney General Jeff Sessions — and because the events were unprecedented in their experience.

McCabe was deputy director under Comey. When Trump fired Comey on May 9, McCabe became the acting director of the FBI. A 20-year veteran of the bureau, McCabe began his career in the New York office, where he worked organized crime cases and was part of an FBI SWAT team. Later, he worked on counterterrorism, counterintelligence, and national security issues, experience that allowed him to become deeply immersed in the Russia probe.

McCabe has testified to the Senate Intelligence Committee that as deputy director, he had “an oversight role over all of our FBI operational activity, including that [the Russia] investigation.”

The Trump administration said at one time that McCabe also was one of a number of potential candidates it was considering to replace Comey. He no longer appears to be a top candidate for the job.

One of the trio will speak to senators on Wednesday

McCabe is scheduled to testify Wednesday before the Senate Intelligence Committee, along with Deputy Attorney General Rod Rosenstein, Director of National Intelligence Dan Coats, and National Security Director Adm. Mike Rogers, all one day prior to Comey’s hearing before the same senators.

Republican senators on the committee reportedly are poised to question McCabe as to why neither he nor Comey informed the Justice Department about President Trump’s efforts to shut down the Russia investigation. On Thursday, they plan to grill Comey on the matter as well. Republicans have indicated they will argue if Trump actually did anything potentially outside the law — yet Comey never informed anyone at the Justice Department about it — that would raise serious questions about Comey's credibility as a potential witness against Trump.

It is unclear whether McCabe will answer questions on his private conversations with Comey about whether to tell the Justice Department about Trump’s alleged pressure of the former FBI director. The new special counsel might believe that such information is pertinent to his investigation, and it is possible that Mueller has asked McCabe not to discuss the issue.

Mueller, himself a former FBI director, may have a bias in believing the word of Comey and other FBI managers over that of Trump. Comey and Mueller became professionally close, and also personal friends, while Comey was the deputy attorney general for part of the Bush administration and Mueller was FBI director. Comey succeeded Mueller in the job.

When he appointed Comey, then-President Barack Obama cited a 2007 confrontation that Comey had with senior officials of the Bush administration. President George W. Bush’s then–chief of staff, Andrew Card, and then–White House counsel, Alberto Gonzales, sought a reauthorization of the administration’s warrantless wiretapping program by then-Attorney General John Ashcroft, who was in the hospital at the time, barely coherent, and recovering from surgery.

Ashcroft, Comey, and Mueller believed that portions of the program were illegal. Comey and Mueller raced to Ashcroft’s hospital room to warn him not to sign the authorization. All three men considered resigning in protest if the program were reauthorized. Bush agreed to modify the program to bring it into compliance with the law.

During the incident, Card summoned Comey to meet him at the White House. In a harbinger of current events, Comey only agreed to go if he could bring a witness, then–Solicitor General Ted Olson.

When the controversy became publicly known, Card and Gonzales claimed that Comey and Mueller’s accounts were untrue. Yet when the Justice Department’s inspector general investigated the matter, Card and several other Bush administration officials declined to speak to investigators at all.

When the inspector general interviewed Comey and Mueller, both men served as witnesses for each other, corroborating in part one another’s accounts. Investigators concluded their accounts were truthful and accurate.

This was largely because both men kept detailed, contemporaneous, and at times even legible notes on the incident. It was also because both men gave investigators the names of subordinates — as many as a half-dozen for each of them — who were themselves involved in the events, or who were told about them by Comey and Mueller shortly after the fact.

Murray Waas is an award-winning investigative reporter