In her 3½ years as Atlanta police chief, Erika Shields appeared to have struck a balance rare in American law enforcement. Known as a staunch ally of police officers who worked closely with unions, Shields simultaneously championed progressive policies such as levying lengthy suspensions in use-of-force incidents and mandating that body cameras be on at all times.

Shields resigned hours after a white officer shot and killed Rayshard Brooks, who was black, on Friday night after a DUI stop. Shields said in a statement that she stepped aside “for the city to move forward and build trust between law enforcement and the communities they serve.”

Shields, who was one of the first American police chiefs to walk with protesters after the death of George Floyd in Minneapolis, is described by allies as one of the most progressive law enforcement leaders in the country, a force for transparency in policing and reducing the use of force.

Now, after the Brooks killing, she has stepped down amid outcry and sorrow — and two weeks of controversy and calls for her resignation after police used less-lethal weapons on protesters and two college students were Tasered and forcibly removed from their car.

Shields is the second police chief to no longer be on the job amid calls for police reform after Floyd’s death. Louisville Police Chief Steve Conrad was terminated earlier this month after the police-involved killing of the owner of a barbecue restaurant. Conrad had been under fire since Breonna Taylor, a 26-year-old EMT, was shot and killed after police entered her apartment on a no-knock warrant in March.

The tenures of police chiefs like Shields who model themselves as reformers can often be short — and lead some to wonder whether the changes they put in place will stick.

Thomas Manger, former chief of the Montgomery County Police Department and past president of the Major Cities Chiefs Association, thinks Shields’s departure will have a chilling effect on reform efforts down the road.

“It becomes more difficult for police chiefs who take over during these turbulent times when they see good police chiefs like Erika stepping down,” Manger said. “You think, my God, here’s somebody doing all of the right things, but because of an incident involving one of her cops, she’s not here.”

This month in Atlanta, during protests against police brutality, civil rights leaders affiliated with Black Lives Matter and the Georgia NAACP criticized the department’s use of force to clear streets, including the incident with the college students. Fulton County District Attorney Paul Howard criminally charged six officers who allegedly used Tasers on the students after smashing the windows of a car and pulling them from the vehicle after curfew. Four of the officers were fired.

Brooks, 27, was killed outside a Wendy’s. According to a preliminary report from the Georgia Bureau of Investigation, officers were called to the restaurant after a complaint about a man asleep in a car at the drive-through. Officers performed a field sobriety test on the man, later identified as Brooks. After he failed the test, officers attempted to place him in custody. The situation escalated and Brooks grabbed an officer’s Taser and ran. Video appears to show Brooks turning back toward the officer and pointing the Taser, and the officer is seen drawing his gun and firing at Brooks. The officer who shot Brooks was fired.

Shields voluntarily stepped down less than 24 hours later. Atlanta Mayor Keisha Lance Bottoms (D) said Shields will continue to work for the department in a job to be determined. Shields and Bottoms’s office did not respond to requests for comment.

The Rev. James Woodall, president of the Georgia NAACP, thinks Shields should have been fired. He said the organization is not satisfied with a job change.

“Anything less than her firing is insufficient,” Woodall said. “We’ve seen the continuation of police violence against black people in this city for way too long. This is not an isolated incident. We had adequate training and we had citizen review boards. We got all of those things that always seem to be recommended in these moments. But still, yet again, here’s another murder of another Atlanta citizen.”

Woodall is calling for an investigation into the culture and practices of the entire department.

“If you don’t do that,” he said, “if you just bring somebody and make them the face of the Atlanta Police Department, and there has not been a culture change, you will have the exact same problems and end up right back in the same situation.”

Shields, a former stockbroker in Boston, moved to Atlanta in 1994 and climbed the ranks of the Atlanta force after patrolling some of the city’s most impoverished communities. She was named chief in 2016, becoming the second woman and only openly LGBT person to lead the department. Shields successfully fought for pay raises for officers and leaned on programs that prioritized use of social services over imprisonment.

In January, Shields suspended police car chases, arguing that the risk to the officer, everyday people and the suspect outweighed the benefit of apprehension. Shields then sent a trove of data on Atlanta police chases over the past three years to the Police Executive Research Forum, a nonprofit that studies policing techniques and trains law enforcement leaders.

“No police chief has ever done that,” said Chuck Wexler, the group’s executive director. “But she looked at everything that happens with police chases and made that unprecedented decision.”

Wexler said he spoke with Shields on Saturday night and again Sunday morning. She told Wexler the incident with the college students and Brooks’s death forced her to consider resignation. Wexler said Shields told him it was her idea to quit.

“She just felt like this was the right thing to do, to step down, that it might help quell the anger in some ways if by her taking responsibility and stepping down,” Wexler said. “That’s the kind of person she is. She was not asked to do so by the mayor. She did this on her own.”

Atlanta police Capt. Stephen Zygaj, the former president of the Atlanta Police Union, said Shields emphasized community policing and developing relationships with citizens, “instead of walking around like Darth Vader’s [Stormtroopers],” he said. Shields earned the respect of the rank and file, Zygaj said, when she successfully lobbied in 2018 to raise pay for officers, typically a pursuit led by union bosses, not police chiefs.

“We never had a chief fight to get officers paid like she did,” Zygaj said.

Adam L. Wilson, a former police officer and author of the book “Tactical Reload: Strategy Shifts for Emerging Leaders in Law Enforcement,” interviewed Shields extensively for the book, and described her as one of the most progressive police chiefs in the country, especially in the realm of officer discipline.

“No policy can alleviate human error completely, but I think she was doing everything she could to mitigate it,” Wilson said.

In 2017, Shields punished Officer Quinton Green with a 20-day suspension for using his fists in a struggle to subdue a man suspected of preparing to smoke crack cocaine. No drugs were found on the man.

“These people calling for her firing obviously didn’t spend any time studying what she had done or what she stood for,” Atlanta Police Union President Ken Allen said.

In a statement calling for Shields’s dismissal, the NAACP cited over-policing of Atlanta’s minority communities.

“At this time, we must address the oversaturated police presence in Georgia’s Black communities,” the statement read. “This is not the first time a Black man was killed for sleeping. The Atlanta Police Department has a history of antagonizing our Black communities.”

Woodall said he never met Shields but knew she had a relationship with other members of the organization.

“In many respects, I pay due deference to her and her leadership,” Woodall said. “However, the fact is that there are still people dying. I think people are missing that. We can do all the reforms and all the piecemeal solutions we want. But at the end of the day, people are still dying. There has to be accountability.”