The former acting FBI director, Brian Driscoll, who pushed back against the Trump administration’s efforts to identify agents who worked on the January 6th investigation, was among a wave of forced ousters aimed at several high-ranking officials, many of whom were involved in separate Trump investigations, on Thursday. 

Also ousted was the assistant director in charge of the Washington Field Office, Steve Jensen, and a special agent, Walter Giardina. In 2022, Mr. Giardina arrested the White House trade advisor, Peter Navarro, at Reagan National Airport on charges of contempt of Congress, to which Mr. Navarro at the time called Mr. Giardina and another special agent “kind Nazis.” Mr. Navarro was sentenced for four months in prison for resisting the Democrat-controlled January 6 committee.

In April, Mr. Jensen was promoted by the FBI director, Kash Patel, and his deputy, Daniel Bongino, to run the FBI’s Washington office, a move that rankled a group of former FBI agents who refer to themselves as “The Suspendables” over Mr. Jensen’s involvement in the FBI’s January 6 investigation. The Suspendables had been suspended or dismissed for a variety of reasons , including refusing to work the January 6th investigation and opposing vaccine mandates.

In response to the firings, the FBI Agents Association said in a statement that it was “actively reviewing all legal options to defend our members.”

“If these Agents are fired without due process, it makes the American people less safe. Agents need to be focused on their work and not on potentially being illegally fired based on their assignments,” the FBIAA said in a statement.

During a sit-down interview with FOX News in May, Messrs. Patel and Bongino defended Mr. Jensen’s promotion despite his role in what the host, Maria Bartiromo, called “the FBI’s overzealous January 6th investigation.”

“That man was in a position where he literally fought back against the machine who was saying, we want to politicize this event,” Mr. Patel told Ms. Bartiromo in May. 

“Steve Jensen and other folks were promoted because they embody what the American public demands of FBI agents,” Mr. Patel told Ms. Bartiromo.  

But now, Mr. Jensen is out.

In his farewell note to FBI colleagues, Mr. Jensen, a 19-year bureau veteran and a father of ten children, according to a former colleague, wrote that he was informed of his dismissal on Wednesday night and intended to meet this challenge “with professionalism, integrity, and dignity.”

“Never waver in your resolve to answer the call to protect the American people and uphold the Constitution. Continue to be bold and aggressive in the pursuit of justice. Most importantly, stay safe and take care of each other.

Be the FBI,” Mr. Jensen wrote.

Mr. Driscoll served as acting director prior to Mr. Patel’s confirmation in February. In February, Mr.  Driscoll resisted helping former acting deputy attorney general, Emil Bove, in identifying those FBI employees who were involved in the January 6th investigation and declined to dismiss eight senior executives on the Justice Department’s urging. 

Mr. Driscoll, who is in his mid-40s, is not yet eligible for retirement. 

In an internal email obtained by NBC News, Mr. Driscoll confirmed to his colleagues that Friday would be his last day with the FBI.

“I understand that you may have a lot of questions regarding why, for which I currently have no answers. No cause has been articulated at this time,” Mr. Driscoll wrote in his email.

“Our collective sacrifices for those we serve is, and will always be, worth it. I regret nothing. You are my heroes, and I remain in your debt,” Mr. Driscoll added.

In May, Senator Grassley, a Republican of Iowa, released a trove of internal emails from Mr. Giardina and other FBI agents involved in the arrest of Mr. Navarro, claiming they were evidence of longstanding “political rot” within the bureau. 

“Instead of focusing on the rampant cases of murder and rape perpetrated against everyday Americans, personnel in the FBI’s Washington Field Office and D.C. U.S. Attorney’s Office were obsessing over ways to target President Trump and his allies. Their conduct is disgraceful and un-American,” Mr. Grassley said in May.

In a text to the Sun, an FBI spokesman declined to comment. An FBI spokeswoman based in the bureau’s Washington field office also declined to comment.