“People from around the world watched the videotape of a man, unarmed and unprovoked, being beat to death by officers of the law,” said Mr. Sharpton, speaking at the Mason Temple, the church where the Rev. Dr. Martin Luther King Jr. gave his final speech the day before he was assassinated.

“We talk a lot about gang bangers in the streets and what colors they wear,” he added. “In Memphis, it looks like they wear the blue color, that uniform.”

Other speakers echoed Mr. Sharpton’s call for stronger federal laws to regulate the police and increase accountability. It had been more than two years since the death of George Floyd, said Bishop Talbert W. Swan II of the Church of God in Christ, and yet lawmakers had not promised changes to the law.