The reasons for Oakland Police Chief Anne Kirkpatrick’s shocking dismissal became clearer Friday, as the head of the city’s Police Commission said she and colleagues determined the chief was withholding information from the oversight authority and failing to increase compliance with federally mandated court reforms.

Commission Chair Regina Jackson said the decision to fire Kirkpatrick without cause on Thursday was “thoughtful” and “didn’t come quickly.”

“When you don’t have confidence in such an incredibly important responsibility, that person really can’t be effective,” Jackson said. “So, we had decided amongst ourselves that we definitely had come to that conclusion.”

Jackson said no “one thing” led to the firing of the city’s first female chief. Instead, the commission’s unanimous closed-session vote to remove Kirkpatrick came after a series of notable events and a methodical process to document deficiencies in closed-door meetings starting five months ago.

One example Jackson pointed to occurred last summer, when the Police Department requested to buy a second bulletproof BearCat, an armored vehicle.

“We asked questions about how was the BearCat deployed, where was it deployed,” she said. “We wanted to understand the processes that went into putting the BearCat on the street, and we are still waiting for those answers.”

The department’s request for a BearCat was rejected.

Also last year, a court monitor determined Oakland police were losing ground in their 17-year struggle to reform the department after the Riders scandal, in which officers allegedly beat up and planted evidence on residents in the city’s poorest neighborhoods.

In March, federal monitor Robert Warshaw admonished the chief over the fatal 2018 police shooting of Joshua Pawlik, and he called an internal investigation — overseen by Kirkpatrick — “deficient in several ways.” Kirkpatrick, as well as the department’s Executive Force Review Board, cleared the four officers who fired their weapons of wrongdoing.

And in December, Warshaw issued a scathing report that accused the department of falling out of compliance in reviewing use-of-force incidents.

Over the past two weeks, commissioners contacted Mayor Libby Schaaf and met with her to discuss their decision to fire Kirkpatrick.

“Initially, she was shocked,” Jackson said. “I think as she spent time with it and heard more about what our concerns were, she understood better.”

A day after the commission’s announcement, Schaaf told a graduating class of the city’s newest officers that the firing was in the “best interest of Oakland,” and “leaders will come and go.”

Dressed in black, Schaaf took the podium Friday morning at the Scottish Rite Center in a graduation ceremony for the force’s 183rd academy of recruits. She gave a speech of hope, but the tense, solemn mood of the veteran officers in the room was palpable.

“It cannot be ignored that you join our department on an interesting day, a day we have changed leadership,” Schaaf said. “And I want to be perfectly honest with you, that my decision yesterday was extremely personally difficult for me. But I made it because I believe it was in the best interest of Oakland.”

Schaaf said a nationwide search will take place to replace Kirkpatrick, and four candidates for the job will be selected by the Police Commission, according to the City Charter. The mayor will then appoint a person from that pool of candidates.

“We will want some demonstrated progressive thinking, certainly emotionally intelligent leadership,” Jackson said. “Someone that has some experience with the reduction of disparities we noticed still exist, and someone that can work to build trust in the community. That will be very, very important.”

On Friday, the Police Department was in a “deep sense of depression,” said Barry Donelan, president of the Oakland Police Officers’ Association. He said the firing gives the message that “if you stand up like Chief Kirkpatrick did ... you could lose your job.”

Donelan criticized the commission and called the board members “antipolice.”

“Right now, I’m doubting my faith in anyone who is an elected official at City Hall and a member of the Police Commission,” he said. “Who is going to come here in this environment?”

The commission held its first closed-session meeting to discuss a performance evaluation of a public employee in July. The commission continued to discuss the dismissal of a public employee for months, but no decision was made on Kirkpatrick’s job status until Thursday evening.

During that time, the commission hired a private attorney and was “essentially building a case” against Kirkpatrick, said Rashidah Grinage, a member of the Coalition for Police Accountability and a longtime critic of Kirkpatrick.

“Some of her interactions have been less than respectful, and it would actually be considered insubordinate,” Grinage said. “So, I think the fact that this commission had power over her was not something that was comfortable for her.”

Tensions flared between Kirkpatrick and Ginale Harris, a member of the Police Commission, at an October meeting in which Harris called a police staffer’s presentation on steps the department was taking to hire women of color “disgraceful.” Kirkpatrick demanded an apology.

“She will not get one from me,” Harris responded. “And neither will you.”

When asked whether he was surprised by the commission’s decision to fire Kirkpatrick, Councilman Noel Gallo said, “Hell yeah.” He said the way in which Kirkpatrick was dismissed was “uncalled for.”

“When you terminate someone, you terminate them for a reason, for a cause,” Gallo said. “The calls and the emails I’m getting (from constituents) is basically … we’ve gone from being a City Hall to being a silly hall.”

Kirkpatrick’s firing will “make it very difficult” to attract a new chief, he added.

“Not only do you have the City Council, you have the mayor, now you have the Police Commission all in charge of your supervision, so that’s going to be very difficult,” Gallo said.

The Oakland Police Commission, which consists of seven civilians nominated by the mayor and a community panel, voted to fire Kirkpatrick without cause, which means she will be paid a full year of salary beyond her termination. When she was hired in 2017, Kirkpatrick’s total compensation was $299,675, including salary and benefits.

Darren Allison, previously an assistant chief, was selected to serve as acting chief until an interim chief is selected.

In Oakland, the mayor, city administrator and Police Commission have the authority to fire the police chief. The commission can remove the chief if it has cause with five votes, according to the City Charter. Without cause, however, the commission needs the approval of the mayor.

With some limitations, the commissioners also have the authority to discipline officers and help craft policies within the department.

Kirkpatrick became Oakland’s first female police chief after being appointed by Schaaf in January 2017 amid allegations that a group of officers had sexual relations with the teenage daughter of an Oakland dispatcher. Other officers were accused of helping cover up their misconduct.

Sarah Ravani is a San Francisco Chronicle staff writer. Email: sravani@sfchronicle.com Twitter: @SarRavani