Brian O'Hara resigned Tuesday after a personnel investigation found he likely deleted a contact during a prior internal probe. Mayor Jacob Frey issued a written reprimand for what he called "serious misconduct," including interference in investigations and poor judgment inconsistent with the role's integrity requirements.

O'Hara, who took over the department in 2022 amid crisis following George Floyd's murder, faced 17 additional open personnel complaints. His tenure saw declining violent crime but criticism for rising overtime spending. He previously gained national attention for condemning federal immigration agents' conduct in Minnesota.

Mayor Frey, who had nominated O'Hara for a second term just this month, named Assistant Chief Katie Blackwell as acting chief. The city continues dealing with a force burdened by turnover and community mistrust that emerged after Floyd's killing.