MEMPHIS — Memphis Police Chief Cerelyn Davis had been on the job for only a few months in 2021 when she saw that homicide numbers were rising toward a record. Near her new home downtown, drivers were buzzing wildly through the streets, often late at night. She had a plan to confront the mayhem.

For reckless drivers, she told her team, officers were to focus less on writing tickets and more on an all-out strategy of seizing cars from the most dangerous drivers. Violent offenders needed to be targeted with new urgency. If the state could not take a case to court, she determined, her agency should ask federal prosecutors to take the case instead.

“We all have that understanding about being tough on tough people,” she said at a community event in November of that year.

Two days later, Chief Davis, the first African American woman to lead the department, launched her most ambitious strategy: a new unit named Scorpion — or Street Crimes Operation to Restore Peace in Our Neighborhoods — would deploy some 40 officers as a strike team in some of the most volatile corners of the city.

Before long, some residents complained of heavy-handed tactics, of officers from the new Scorpion team employing punitive policing in response to relatively minor offenses. Then came the arrest and killing of Tyre Nichols, and video footage released on Friday that showed how officers kicked, punched and used a baton to beat Mr. Nichols as he pleaded with them to let him go home.

With five officers charged with murder, community leaders are now trying to assess how a unit that was supposed to ease the violence in Memphis had instead inflicted an attack so brutal that Chief Davis herself called it “heinous” and “inhumane.” The city announced the disbanding of the unit on Saturday, and Chief Davis has called for a review of all her department’s specialized units.

“We still want crime addressed in our communities, but we don’t need to kill innocent people to do it,” said Van D. Turner Jr., a mayoral candidate who is president of the city’s N.A.A.C.P. branch and who served on the recent mayoral advisory council for “reimagining policing.”

The city had for months touted the Scorpion team as key to its crime-fighting strategy, promoting it as nearly an overnight success at a time when the city was posting record homicide numbers. Memphis recorded more than 300 murders in 2021; by comparison, New York City, which is 13 times larger, had fewer than 500.

Just a few days after the Scorpion unit was unveiled, one local television report noted that the Memphis police credited it with making more than 30 arrests, and seizing at least 29 guns and nearly 170 grams of marijuana.

Scorpion’s supposed successes became a talking point for city officials, including Mayor Jim Strickland, who highlighted the unit during his January 2022 State of the City speech and listed its early accomplishments: 566 arrests, 390 of them for felonies, as well as seizures of $103,000 in cash, 270 vehicles and 253 weapons.

As she marked her one-year anniversary on the job in May 2022, Chief Davis gave a presentation to the City Council in which she noted some progress in curtailing crime. In a slide titled “CRIME REDUCTION,” the Scorpion unit was her first bullet point.

“We created the new Scorpion unit,” she said, adding: “This unit basically targets some of the hot-spot areas where we saw frequent aggravated assaults and high crime.”

Like much of the country, Memphis had seen its homicide numbers jump in 2020 and 2021. Those numbers eased somewhat last year, but it was not clear how much credit could be given to the Scorpion unit, as many cities also saw declines in 2022. Memphis recorded a rise in property crimes last year.

Some activists and community members had been wary about the operations of the Scorpion unit long before the attack on Mr. Nichols.

Hunter Dempster, an organizer with Decarcerate Memphis, a group pushing for accountability in the criminal justice system, said on Sunday that his organization has long been warning about the Scorpion team. He said the unit’s main mission had appeared to be conducting mass pullovers in poor neighborhoods that are home to many people of color.

He described the officers in the unit as “violent” bullies and said many residents had also questioned why the unit often used unmarked vehicles, “regular cars that you would never think were police.”

In any case, he said, people were prepared for trouble whenever a Scorpion unit conducted a traffic stop.

“If you get pulled over, you know that there’s potential for violence,” he said. “That’s how terrified the general public is of these units.”

Such debates have echoed in cities around the country, with a number of cities once again setting up specialized units to aggressively target offenders in high-crime neighborhoods during the pandemic — in some cases, this happened in cities that had disbanded such units in past years when concerns rose over the units’ tactics or outcomes.

In 2020, for instance, the New York Police Department disbanded the aggressive squads known as “anti-crime units” that had patrolled the city, often in plainclothes. Such teams, tasked with focusing on getting guns off the street, had conducted an outsize share of gun arrests. But they were also responsible for a disproportionate number of stop-and-frisks, as well as police shootings. Last year, the new mayor, Eric Adams, himself a former police commander, revived a version of these units, though officers now wear modified police uniforms, rather than street clothes.

Mr. Adams was one of a number of local politicians around the country who won election over the past two years after running on get-tough-on-crime platforms.

Lawyers representing Mr. Nichols’s family have called on federal officials to investigate hot-spot police units, saying that they often operate with impunity, oppressing young people and communities of color. Antonio Romanucci, one of the family’s lawyers, said that while the intent of the unit was good, the result was a failure.

“This Scorpion unit was designed to saturate under the guise of crime-fighting, and what it wound up doing instead was creating a continual pattern and practice of bad behavior,” he said. The lawyers said they had heard of other cases before Mr. Nichols’s death in which the Scorpion unit had used excessive force.

In laying out her crime-fighting strategy in 2021, Chief Davis spoke in particular about reckless driving in Memphis, calling it the worst she had seen in her career and expressing fear about being on the roadways herself.

The city had been dealing with drag racing and stunt driving. On a Saturday night in late November, all four lanes of traffic were blocked on Interstate 240 when two drivers began doing doughnuts on the highway, with a number of onlookers recording the activity on their phones. Local officials used the incident as ammunition to call for more legal leeway to seize violators’ cars.

“We have advocated: Take the car,” Chief Davis said in 2021. “Even if the case gets dropped in court. We witnessed it. You did it. You might be inconvenienced for three days without your car. That’s enough.”

The police said they stopped Mr. Nichols on the night of Jan. 7 on suspicion of reckless driving, though Chief Davis later told NBC News that the department had been unable to find evidence for why he had been stopped. Video showed officers surrounding Mr. Nichols’s vehicle at an intersection, cursing at him and pulling him out of the driver-side door. Mr. Nichols spoke in calm tones, seemingly trying to de-escalate the situation, as officers continued to curse and yell.

After police officers beat him, he was eventually taken to the hospital in critical condition. Mr. Nichols died three days later. His family’s lawyers said an independent autopsy found that Mr. Nichols “suffered extensive bleeding caused by a severe beating.”

In the wake of the announcement on Saturday that the unit would be disbanded, some city officials said they wanted to take a look at what marching orders the unit was given when it was created.

“We were all tripping over ourselves to give them compliments because we have a violent crime problem and drag racing problem,” said one member of the City Council, Worth Morgan. “But it was done under the pretext that they would protect and serve and not violate anyone’s rights, and these officers did in a hugely problematic way.”

Another council member, Frank Colvett Jr., said he had not heard complaints about Scorpion before Mr. Nichols’s death but agreed with the decision to disband it.

“I support shutting the unit down until we know more about their recruiting and exactly how they are trained,” he said.

On Sunday, a group of about a dozen protesters were gathered outside the Memphis Police Department’s Ridgeway Station for the third consecutive day of protests.

At the demonstration, Casio Montez said in an interview that deactivating the Scorpion unit was a positive first step but that organizers also wanted another anti-crime unit — a special operations team focused on illegal drugs — to be disbanded.

Mr. Montez said that he had been stopped by the Scorpion unit in the past, including once when he said he was “roughed up” by officers on the unit.

“It wasn’t frightening,” Mr. Montez said. “I just know it was unjustified.”

Mr. Montez, who is Black, said that his experience in encounters with the unit is that the officers “only escalate the situation.”

“They get out on a situation that is probably a Level 3, but they get out of the car like it’s a Level 10,” Mr. Montez said. “So at the end of the day, we have to disassemble the whole department and build it back up. Until we do that, there’s going to be another Tyre.”

Jessica Jaglois contributed reporting. Julie Tate contributed research.