In the months before President Donald Trump fired FBI Director James Comey, FBI counterintelligence agents investigating Russian election interference were also collecting evidence suggesting that Trump could be compromised by Russian President Vladimir Putin.

Andrew McCabe, the former FBI deputy director who oversaw the bureau’s Russia investigation, told me in an interview conducted late last week that concerns about Trump had been building “for some time”—and that he was convinced the FBI would have been justified in opening a case against the president.

“We felt like we had credible, articulable facts to indicate that a threat to national security may exist,” McCabe told me. And FBI officials felt this way, he said, even before Trump fired Comey. That firing set off a chain of events that, as McCabe put it, turned the world “upside down.” McCabe wrote contemporaneous memos describing “key” conversations he had during that chaotic period—with the president, with Deputy Attorney General Rod Rosenstein, and others—that are now in the hands of Special Counsel Robert Mueller.

McCabe’s new book, The Threat: How the FBI Protects America in the Age of Terror and Trump, is not generally overstated in its approach to Trump. This reflects either an aversion to exaggeration on McCabe’s part—his self-image, it seems, is that of a just-the-facts-ma’am G-man—or an awareness that the Justice Department’s inspector general has, for all intents and purposes, branded him a fabulist, a charge he finds particularly wounding. McCabe, who was fired in March 2018, told me he’ll be filing a lawsuit against the Justice Department that will challenge the circumstances of his termination, which was ostensibly based on the inspector general’s findings that he had leaked information to the media without permission. In person, McCabe still seems awed by the “series of head-scratching, completely shocking events” that he witnessed two years ago.

The bulk of McCabe’s book has little to do with Trump. Much of it focuses on his time working on counterterrorism cases and as the head of an interagency team founded by President Barack Obama to reevaluate the country’s torture practices. Perhaps in a nod to the arc of his career, though, it begins and ends with Trump—McCabe spent his first 10 years at the bureau in New York City, investigating Russian organized crime.

“It has occurred to me on a number of occasions that, you know, Donald Trump and I know some of the same people,” he told me.

Our conversation has been edited for length and clarity.

Natasha Bertrand: You don’t talk in the book about the discussions that took place about “wearing a wire” into the Oval Office or invoking the Twenty-Fifth Amendment to remove Trump from office. But you’ve since confirmed that these discussions took place in the days after Comey’s firing in May 2017. What made you and other officials so concerned about Trump’s ability to be president, about his fitness to serve?

Andrew McCabe: Neither issue is mentioned in the book because I felt like both were so inflammatory and could become very distracting. The Twenty-Fifth Amendment conversation was really nothing more than that. It was something Rod [Rosenstein] brought up off the top of his head in the overall context of thinking about what the president’s intentions were in firing the FBI director and asking us to drop this case. At no time did I think that there was actually an effort under way to invoke the Twenty-Fifth Amendment or remove the president. I heard it discussed, but there weren’t meetings about it. It was simply a comment that Rod made. And I think it’s illustrative of the conditions we were trying to navigate at the time. It was absolutely crazy. The world was upside down.

Bertrand: Rosenstein really seems to have taken the lead here in throwing out these highly controversial ideas—wearing a wire, invoking the Twenty-Fifth Amendment, etc. How do you square that with his writing the memo that was used later by Trump to justify Comey’s firing?

McCabe: It was a huge conflict, and one that I struggled with at the time. Rod is the guy that volunteered to write the memo firing Jim Comey, and then, in the days after, he asked me to put him in touch with Jim Comey to discuss the special-counsel selection. So these things were in complete conflict. But at the time, I had to focus on the work we knew we needed to get done and needed to get done quickly. What was important to me was to ensure that we got a special counsel appointed and we put the investigation on as solid ground as we could.

Bertrand: Before Robert Mueller was appointed, Trump met with the Russian ambassador and foreign minister in the Oval Office, where he disclosed classified information. How did you react when you found out about that conversation?

McCabe: It was the latest in a string of head-scratching, completely shocking events. For counterintelligence investigators, the idea that the American president would have a Russian foreign minister and his media into the Oval Office and that he would make a comment like that—a comment that so clearly undermined the effectiveness of his chief law-enforcement and intelligence agency—was just confounding.

Bertrand: That reminds me of a passage that jumped out at me in your book: “He thought North Korea did not have the capability to launch such missiles. He said he knew this because Vladimir Putin had told him so … the president said he believed Putin despite the PDB [Presidential Daily Briefing] briefer telling him that this was not consistent with any of the intelligence that the US possessed.” How do you explain that?

McCabe: It’s inexplicable. You have to put yourself in context. So I am in the director’s chair as acting director. My senior executive who had accompanied the briefer to that briefing, who sat in the room with the president and others, and heard the comments, comes back to the Hoover Building to tell me how the briefing went. And he sat at the conference table, and he just looked down at the table with his hands out in front of him. I was like, “How did it go?” And he just—he couldn’t find words to characterize it. We just sat back and said, “What do we do with this now?” How do you effectively convey intelligence to the American president who chooses to believe the Russians over his own intelligence services? And then tells them that to their faces?

Bertrand: Does this strike you as the behavior of someone who’s compromised?

McCabe: I mean, it certainly could be. I don’t know that for a fact. That was the reason we initiated the [counterintelligence] investigation. We were concerned, and we felt like we had credible, articulable facts to indicate that a threat to national security may exist. And, in fact, that a crime may have been committed: obstruction of justice. My own view of it is that those two things, the obstruction and the national-security threat, are inextricable. They are two sides of the same coin. To not have opened a case under those circumstances, particularly because the person who’s the subject of that investigation is the president, would have been a complete abdication of our responsibilities.

Bertrand: How would you respond to criticism that when the counterintelligence investigation into the president was opened, the FBI’s judgment was clouded because emotions were running so high in the aftermath of Comey’s firing?

McCabe: I could see how that would fit if we had initiated this concern in the wake of Jim’s firing. The fact is, we were building to this point for months before Jim was fired. We had several cases already open under the umbrella investigation of the Russia case … and the concern about the president and whether or not he posed a national-security threat that we should be investigating had been building for some time. But it was the events around the firing that kind of sealed the deal for me and the folks on the team.

Bertrand: The sense I get from your book is that you sometimes wish you had more forcefully confronted the president when you had the chance, especially after Comey was fired and Trump was pressing you to say that everyone at the bureau was happy about it.

McCabe: I mean, I’ve spent a lot of time thinking about how I reacted in those incredibly strange moments and what I said, and I tried to be honest in the book about that kind of reevaluation that you can only do in hindsight, right? But if I had to do it all over again, I’d probably do it just the same way. I was trying desperately to keep a large, distraught organization on its feet and moving forward. And provoking a fight with the president of the United States was not going to be helpful in kind of calming those waters and keeping everybody and getting back to work. I also would not agree with his repeated insistence that everybody was happy about Jim being fired. I would not agree to that under any circumstances.

Bertrand: Some question now why the public should believe your recollection of events when the Justice Department’s inspector general concluded last year that you had lacked candor when describing your interactions with the press. How would you respond to that?

McCabe: It was very hard to leave the organization that I loved, and still love to this day, under those circumstances. To spend 21 years as an FBI agent, living under the ideals of fidelity, bravery, and integrity, and then to be branded a liar the day before you were gonna retire. It was very tough. But in some ways, it’s also entirely predictable. The facts are that this president has a long and illustrious history of attacking the credibility of people who say things that he doesn’t like, and I believe strongly that that’s what’s happened here. Firing me for lack of candor was a perfect way to undermine my ability to, who knows, provide testimony against him, to tell these stories that I’ve now told in the book. I never, ever intentionally misled the FBI inspection division, the office of the inspector general, or any director of the FBI, ever. Not ever. I completely reject the findings, the conclusions, and the recommendations in that [inspector general] report. I am very familiar with investigative reports. I’ve been writing them and reading them for 21 years. That is not an investigative report. That was a pretext to reach the conclusion that was being demanded by the president of the United States.

Bertrand: And how would you respond to the criticism over the Russia investigation being kept a secret from voters in 2016, even though the Clinton email investigation was not? Do you regret not disclosing more about what was known before the election?

McCabe: No. I see how, on kind of a headline level, there appears to be kind of a fundamental disparity there. I don’t deny that. But you have to really get into the circumstances and the context of each investigation. The Clinton investigation was public before we even got it. The referral to the FBI was public, so we initiated our investigation, and very quickly thereafter the attorney general and Director Comey acknowledged it publicly. The whole world was kind of screaming for that conclusion as we got closer and closer to the election. The Russia investigation was very different … Counterintelligence cases are investigations best pursued quietly, and especially in the lead-up to the election, the idea that we would’ve gone forward with something that we didn’t know we had—I don’t regret handling it the way that we did.

Bertrand: Shifting gears now to the special-counsel investigation, legal experts have often observed that Mueller seems to be investigating Trump and his campaign like he would a Mafia family. You spent a decade going after the Russian mob in New York. Do you think, given what we’ve seen from Mueller so far, that Trump is still a target?

McCabe: There are a lot of patterns in what Director Mueller is doing that are very familiar to me. Those patterns of targeting and investigating people who may have had more of a hands-on role, albeit at a lower level, and using those investigations to develop information and informants and cooperators—I mean, it is really the classic enterprise investigation that Director Mueller and his team have pursued. So do I think the case into Trump is open or closed? There’s absolutely no reason for me to believe that it’s closed. And you can certainly look at what Mueller’s done so far to say he is doing exactly what we would do with the investigation of a cartel or an organized-crime family.

Bertrand: So Trump strikes you as someone who runs his organization, and now is running his administration, like the Mob.

McCabe: Well, that was my own experience with him, right? That kind of overwhelming or overriding focus on loyalty and sorting everybody out immediately—like, you’re either with us or you’re against us. Those are all traits that you see in organized-crime enterprises.

Bertrand: Democratic Representative Adam Schiff said in an interview last week that he is concerned the “red line” Trump drew against Mueller examining his finances is being enforced. Having worked with Mueller so closely, do you believe he would be intimidated out of pursuing a key line of inquiry?

McCabe: I know him pretty well. And I have never known him to be intimidated by anything or anyone. He is at heart an investigator, and he is not the kind of investigator who’s going to be brushed off of a potential area of investigation because he’s afraid of provoking the ire of the president, or making somebody mad, or getting too close to the boundaries. He is going to go wherever he thinks he needs to go to find out what happened.

Bertrand: Do you think we’ll ever hear from Mueller? Do you think he’ll come out and explain his findings once all this is over?

McCabe: He’ll explain his findings in the report, and then if he’s called upon to testify about it, he’ll certainly do that. But he is always the guy who will say less than more. He’ll seek less attention than more attention. He is perfectly happy to do his job and to do it fully and completely. And then, when it’s all said and done, he’ll lock the door behind him and go home.