The Minneapolis police chief, Brian O’Hara, resigned on Tuesday after a report found that he probably interfered with an investigation into alleged sexual misconduct.

O’Hara stepped down after a meeting with the Minnesota city’s mayor, Jacob Frey, who earlier this month nominated him to serve a second term after his appointment in 2022 to steady a police department still in turmoil after the murder of George Floyd two years earlier.

Frey issued O’Hara with a “serious misconduct” reprimand after receiving the report on Tuesday, and warned he faced discipline up to and including dismissal, according to the New York Times.

Frey announced O’Hara’s resignation at a Tuesday evening press conference, at which he said he had lost confidence in the chief’s ability to lead.

“Trust is not secondary to the job, it is the job,” Frey said. “When trust is broken it becomes extremely difficult to continue leading effectively.”

The investigation into O’Hara’s conduct found no evidence to confirm allegations he had improper sexual relationships with city employees, the Times said, but concluded he had likely deleted a contact from his phone last year while facing a previous internal investigation, amounting to interference.

“Your behavior, as substantiated by the investigation, demonstrates poor judgment, is inconsistent with the level of integrity this role requires, and has made it extraordinarily difficult for you to continue effectively in your role,” Frey’s letter to O’Hara stated.

O’Hara has not yet commented publicly about his resignation.

The mayor said assistant police chief Katie Blackwell would take over acting leadership of the department until a permanent replacement could be found. Blackwell is expected to be among the candidates.

O’Hara was appointed in November 2022 with a mandate to reform the Minneapolis police department, which had just seen four of its officers sentenced for their involvement in Floyd’s 2020 murder. They included Derek Chauvin, who received a 22.5-year prison term for the killing, and a subsequent, concurrent 21-year term for violating Floyd’s civil rights that saw the former officer moved to federal prison.

A two-year justice department investigation concluded in 2023 that the department engaged in a pattern of excessive force and years of unlawful discrimination against Black Americans.

Frey, at the Tuesday press conference, credited O’Hara with rebuilding public trust in the department, but said that trust needed to extend to the person leading it.

“Everyone makes mistakes, including me, but what I can’t allow is a breach of trust,” Frey said. His comments were a reversal from his position earlier this month when Frey said O’Hara was “the right leader for this moment and for this city”.

Announcing his support for the chief to serve another term, he added: “Minneapolis didn’t ask for small steps, we demanded real, measurable change. And under his leadership, that’s exactly what we’ve been seeing.”

O’Hara is credited with reversing a stem of resignations from the police department, and heading off a call from some Black lawmakers for it to be disbanded, a proposal rejected by voters in 2021.

More recently, he has been a vocal critic of the Trump administration’s immigration enforcement surge into Minneapolis, which saw the deaths of two unarmed US citizen protesters, Renee Good and Alex Pretti, in January by federal officers.

He condemned the shootings in a 25 January appearance on CBS’s Face the Nation, during which he said Minneapolis residents had “had enough” of the violence.

“This is the third shooting now in less than three weeks,” he said. “The Minneapolis police department went the entire year last year, recovering about 900 guns from the street, arresting hundreds and hundreds of violent offenders, and we didn’t shoot anyone.

“And now this is the second American citizen that’s been killed, it’s the third shooting within three weeks.”

The June 2025 murders of Democratic Minnesota lawmaker Melissa Hortman and her husband; and a mass shooting at Annunciation Catholic school in south Minneapolis two months later, also came during O’Hara’s tenure.

Frey said at the 7 May nomination event that the number of Minneapolis police department officers had climbed from 550 to more than 640, applications were up by 200%, and that crime had fallen across the city since O’Hara became chief.

Todd Barnette, commissioner of the Minneapolis office of community safety, recognized those achievements in a statement to the Guardian on Wednesday.

“Chief O’Hara helped advance police reform efforts, replenish sworn staffing and guide the department through some of the city’s most challenging moments,” he said, thanking him for his “commitment” to public safety.

“We will continue moving forward – building trust in our police department through transparency, accountability, and collaboration with community members.”