But the interim chief also faced scrutiny over her department’s response to demonstrations against police violence.

The Minnesota police killing of George Floyd in May triggered Black Lives Matter protests around the country and in Oakland, where activists had urged cuts to the police force for years. During some of the demonstrations in late May and early June, people set 137 fires and vandalized 200 businesses, Manheimer wrote in an open letter to the community. She said the department used smoke and gas to disperse crowds and “stem assaults on officers.”

In July, federal judge Joseph Spero issued a preliminary injunction that limited the Police Department’s use of tear gas and non-lethal munitions, as part of a lawsuit filed by the Anti Police-Terror Project and various people who participated in the protests.

Manheimer acknowledged the “righteous rage” of the demonstrators. However, she said that other people had used the protests as cover for violent disruption.

By mid-summer, cities across the nation were rushing to take action on police brutality and Oakland leaders wanted to set an example. The City Council formed a Reimagining Public Safety task force with a stated goal to cut the department’s $290 million budget in half.

For several months, Manheimer sat in on task force meetings where some participants accused the police of irresponsibly driving up spending with overtime, a complaint echoed by members of the City Council. But when City Administrator Ed Reiskin directed the department to cut overtime in December by disbanding units — such as motorcycle traffic enforcement, foot patrols and a detail that provides security when city workers clear homeless encampments —some city councilmembers were not satisfied, saying they had been shut out of the process.

“It was very frustrating that many tried to paint a picture of the Police Department frivolously overspending their budget,” Manheimer said. “That money was being spent on vital community services. I think that was the thing that was most irksome. There’s not an understanding by our leaders or by the Reimagining Committee that we are so understaffed and under-resourced that everything you cut impacts the safety in our community.”

The city reinstated its police homeless encampment detail, though other services remain suspended.

In January, Manheimer’s last month on the job, Oakland saw 15 homicides. It marked the deadliest start of the year in two decades and a rapid unraveling for a city that spent years chipping away at violent crime.

“We’re talking about real lives, not just statistics,” said City Councilman Loren Taylor, who co-chairs the Reimagining task force. His district includes a large swath of the flatlands in East Oakland, an area bounded by Interstate 580 in the hills and Interstate 880 near the industrial waterfront. Over the past year it became an epicenter of intertwined crises in Oakland: shootings, poverty and a relentless virus.

“Communities and neighborhoods are being traumatized, and we have to address that,” Taylor said. “It would have been a challenge for anyone, let alone an interim chief who doesn’t have the history, the background, the connection to community, everything else.”

Armstrong, who has worked closely with Manheimer throughout her stint as chief, has a strikingly different public image. He is Black, grew up in Oakland and is widely seen as someone with deep community roots.

Yet as he steps in, the Oakland police face at least two internal investigations. One centers on officers who may have endorsed or “been involved” with the social media account of a former officer who defended the Capitol takeover mob. Another concerns six Instagram posts that used racist content to denigrate police reforms.

John Jones III, a formerly incarcerated community activist who serves on the Reimagining task force, said he initially felt skeptical of Manheimer. About two decades ago, Jones was arrested in the Tenderloin by an officer who he said planted drugs on him. Manheimer was working the Tenderloin beat at that time.

Shortly after she took the Oakland job, the two met; Jones brought up the arrest and pointed to what he saw as an injustice. Manheimer said she made several calls to the San Francisco Police Department and the District Attorney’s Office, and that staff offered to work with Jones to expunge the conviction from his record.

Since then, “we’ve been in contact on a variety of issues,” Jones said. “To me, that’s important,” he added, noting that dialogue is the first step toward building trust.

Manheimer agreed.

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan