Days after San Mateo County released a scathing report accusing Sheriff Christina Corpus of abuse of power and other wrongdoing, her acting assistant sheriff, Matthew Fox resigned Thursday, the Sheriff’s Office said.

Fox was promoted to the position in September after Corpus fired his predecessor, Ryan Monaghan. The county report found that Corpus fired Monaghan for cooperating with the independent investigation into her office.

It’s unclear why Fox decided to step down. He did not immediately respond to a request for comment Friday morning. The Sheriff’s Office declined to provide any further information about his resignation.

On Wednesday, Corpus made a shocking appearance before the County Board of Supervisors, in which she assailed the report as “politically motivated, one-sided and filled with lies.”

The 400-plus page report found Corpus, the county’s first Latina sheriff, repeatedly retaliated against officers and employees, used racist and homophobic slurs, and had an inappropriate personal relationship with her chief of staff, Victor Aenlle.

Before supervisors voted to demand Corpus’ resignation and eliminate Aenlle’s administrative position Wednesday evening, Corpus informed the board she had appointed Aenlle as assistant sheriff.

“I am the sheriff of this county, elected by the people of San Mateo County, and I will not be bullied,” she told board members.

The report — authored by retired Santa Clara County Judge LaDoris Cordell — was released just hours after Carlos Tapia, president of the San Mateo County Deputy Sheriff’s Association, turned himself in Tuesday on felony charges related to alleged time card fraud.

In September, Tapia and the union publicly accused Corpus and Aenlle of many of the same claims in the report. Corpus denied the arrest was made in retaliation or was in response to the report.