One of the family’s principal demands was to shut down the Scorpion unit. Anthony Romanucci, one of the family’s lawyers, assailed the unit and others like it that police departments across the country have employed to knock back crime in neighborhoods where it has been persistent.

“The intent was good,” Mr. Romanucci said. “The end result was a failure.”

Mr. Nichols’s death had stirred intense anger and sorrow among many in the community, a pain that only intensified after people were able to watch roughly an hour of footage for themselves.

“I see why he ran — he was scared for his life,” said the Rev. James Earl Kirkwood, the executive director of the Memphis Christian Pastors Network and a retired colonel in the Police Department. “This has set back police relations in Black and brown communities in our city.”

DeVante Hill, an activist in Memphis, said he met with Chief Davis on Friday and presented a list of demands: Reprimand the superior of the charged officers, make investments at the community level to combat crime and completely overhaul training.

When Mr. Hill told Chief Davis that he also wanted Scorpion disbanded, he said her answer was instant and unequivocal: “Done,” she told him.

The decision to disband the unit was announced on Saturday as protesters marched through the city.

“You know what that means?” one of the protesters asked the crowd. “This worked.”

Hunter Dempster, an organizer with Decarcerate Memphis, a group pushing for accountability and fairness in the criminal justice system, called the development a “good start.”

“But it’s not enough,” Mr. Dempster clarified.

“We don’t want another Tyre,” he said. “We don’t want to be out in the streets again, so we’re in it for the long haul.”

Jessica Jaglois, Jesus Jiménez and Mark Walker contributed reporting from Memphis. Mike Baker also contributed reporting.