[2] While chief of the respective departments, crime rates and police response times were reported to have reduced in both, however, in Lubbock, issues arose over the city's 911 system, where the number of "abandoned" calls, calls which were ended before being answered, doubled.

He later admitted that he had been too focused on the dispatch time of answered calls and that he had learned from his previous mistakes.

[1][3] On March 22, 2024, over a year after the firing of previous chief LeRonne Armstrong and a sharp increase in crime in 2023, Mayor of Oakland Sheng Thao announced the appointment of Mitchell, who she described as "a strong leader and a smart crimefighter who delivers results," as chief of the Oakland Police Department to replace acting chief Darren Allison.

As chief, Mitchell announced his intent to go on a "listening tour", where he spoke with officers, officials, and community members.

He also said one of his goals was to remove the department from a two-decade-long federal oversight following a police brutality incident by instituting reforms.