Footage of a traffic stop that has seen five ex-Memphis police officers charged with murder shows them kicking and punching a motorist for several minutes as he cries out for his mother.
Officers are seen beating Tyre Nichols, 29, in the videos from the 7 January arrest, with no signs of him resisting.
US President Joe Biden said he was “deeply pained” by the “horrific” clip.
Lawyers for Nichols’ family likened the assault to the 1991 police beating of Los Angeles motorist Rodney King.
Peaceful protests took place in Memphis on Friday night after the video was released, with some demonstrators blocking a major highway in the city, while small-scale demonstrations were held elsewhere in the country.
Many protesters held banners demanding justice for Nichols and an end to “police terror”.
This article contains descriptions of violence that some people may find distressing
Police initially said Nichols had been stopped on suspicion of reckless driving, which has not been substantiated. He died in hospital three days later, on 10 January.
Nichols was black, as are all five officers charged in the case.
Memphis Police Department released four graphic videos of the traffic stop and its violent aftermath on Friday, totalling more than an hour of footage.
The first clip shows officers pulling Nichols out of his vehicle and shouting at him to get on the ground.
“I didn’t do anything!” he says. Officers demand that he lie down flat.
“Get on the [expletive] ground!” one officer shouts, as another is heard saying: “Tase him!”
An officer shouts: “Put your hands behind your back before I break your [expletive].”
“You guys are really doing a lot right now,” Nichols says to the officers. “I’m just trying to go home.”
Within seconds one of the officers fires a Taser at Mr Nichols, who leaps up and manages to run away.
A separate video, from a CCTV camera mounted on a utility pole, shows officers beating Nichols after catching up with him in a residential area.
Two officers are seen holding Nichols down while others take turns kicking and punching him and striking him with an expandable baton.
They drag him across the ground and prop him sitting up against a squad car. More than 20 minutes elapse until an ambulance is seen arriving.
The third and fourth videos show police body camera footage of the beating, with Nichols being held down, pepper-sprayed and assaulted as he repeatedly shouts: “Mom!”
The videos also show officers milling about recounting details of the incident as Nichols lies slumped against the car.
Some of them claim Nichols “swung” at them or reached for their guns, though neither allegation is clear from the released video.
Officers can also be heard saying that nothing was found in his car.
Nichols’ mother, RowVaughn Wells, has said her son was only about 230ft (70m) from home when Memphis police officers “murdered him”.
Representatives of the family have described Nichols as the father of a four-year-old son and a keen skateboarder who had recently enrolled in a photography class. He worked for the FedEx parcel delivery firm.
One of the lawyers, Antonio Romanucci, said: “This young man, by definition of the law in this state, was terrorised.”
The video is “appalling”, Greg Donaldson, a professor at John Jay College of Criminal Justice in New York, told the BBC.
He said the lack of training stands out, with the police officers’ anger seeming to grow “as their incompetence seems to be more revealed”.
“The worse part of it was the inhumanity after the incident,” he added, as officers leave Mr Nichols “laying there on the ground like a piece of garbage.”