"For [Ohr] to be in the Justice Department, and to be doing what he did, that is a disgrace," Trump added.
But -- even after months of repeated attacks on him from Trump and the president's political allies -- it's still unclear exactly what, if anything, Ohr did.
Trump has attacked Ohr by name frequently in recent months, as his reportedly private fuming over Mueller's probe increasingly seeps onto his Twitter feed. On Tuesday, Trump accused Ohr and his wife, Nellie, of being "in on the act big time" to undermine his presidential campaign in 2016.
Around the same time, backed by money from Democratic operatives, the research firm Fusion GPS hired former British spy Christopher Steele to look into Trump's alleged ties to Russia. Steele was friendly with a Fusion GPS employee's husband – Bruce Ohr, an organized crime expert who was serving as associate deputy attorney general in the Justice Department.
Steele ultimately compiled a "dossier" filled with an array of controversial allegations against Trump. Ohr "wasn't working on the Russia matter," Deputy Attorney General Rod Rosenstein recently told lawmakers. Nevertheless, Ohr gave a copy of the dossier to the FBI - but by then the FBI had already obtained a copy of the dossier from another source.
The dossier helped push the FBI to expand its counterintelligence investigation into whether anyone associated with Trump's campaign may have been coordinating with Russians to influence the 2016 presidential election. And, for a short period then, the FBI was in contact with Steele about his work on the matter.
In October 2016, the dossier was one of many pieces of evidence the FBI used to justify its secret monitoring of Trump campaign adviser Carter Page, who the FBI believed was working as an agent for Russia and who the FBI knew had been targeted three years earlier for recruitment by Russian spies. Page has denied working for the Russians.
The FBI's probe of Russian meddling and possible ties to Trump associates was being run by Peter Strzok, the now-fired FBI veteran. In late 2016 or early 2017, around the same time the FBI decided to cut off contact with Steele, Strzok and Ohr spoke as many as five times about "operational" and "investigative matters," Strzok recently told a House panel.
Citing orders from FBI attorneys, Strzok wouldn't offer any more details about their interactions. But under oath he insisted to lawmakers that the true nature of what Ohr did – when it can be made public – will both "reassure" and "disappoint" concerned Republicans.
It's unclear if Ohr was using those contacts with Strzok to pass information from Steele to the FBI. At the time, Ohr was assigned to work on matters completely unrelated to Russia. A State Department website shows that in October 2017, while still in the deputy attorney general's office, he traveled to Honduras to speak at a forum about security issues facing Central America. But when Rosenstein then learned that Ohr had been in contact with Steele, "we arranged to transfer Mr. Ohr to a different office," Rosenstein recently told lawmakers.
The Justice Department's inspector general is now looking into Ohr's actions, Rosenstein said.
In recent months, many Republicans – led by Trump and a small group of House members – have used Ohr to push their view that Mueller's probe is tainted.
"I think that Bruce Ohr is a disgrace with his wife Nellie," Trump told reporters on Friday. "And Mr. Mueller has a lot of conflicts also."
A source with knowledge of the Mueller probe described such allegations against Ohr as "a fishing expedition."
Before joining the deputy attorney general's office, Ohr served as director for the Justice Department's Organized Crime Drug Enforcement Task Forces. In 2013, the State Department described him as "a Department of Justice subject matter expert" on transnational organized crime.
He had spent several years in senior positions within the department, overseeing gang- and racketeering-related prosecutions.
From 1991 to 1999, he served as an assistant U.S. Attorney in the Southern District of New York.
He also served in private practice, and has a law degree from Harvard Law School, according to government documents posted online.
On Wednesday, when the White House announced it had stripped Brennan of his security clearance, Trump spokeswoman Sarah Sanders said Trump was contemplating whether to strip several others, including Ohr, of their clearances.
At least two of those she mentioned, former FBI director James Comes and former deputy director Andrew McCabe, lost their clearances some time ago.
In response to Brennan's loss of security clearance, a dozen senior intelligence officials -- who served Republican and Democratic presidents -- issued a joint statement, saying, "[T]he president's action regarding John Brennan and the threats of similar action against other former officials has nothing to do with who should and should not hold security clearances — and everything to do with an attempt to stifle free speech."