The US Justice Department has opened an inquiry into the videotaped beating by a dozen police officers of an already wounded suspect in a Philadelphia street.
The videotape from a news helicopter shows the officers - white and black - kicking and beating Mr Thomas Jones (30), a black man accused of shooting an officer and hijacking a police car. He is said to be in a serious condition in hospital with injuries to his abdomen and his arms. The police officer, Mr Michael Livewell (24), was shot in a finger.
Witnesses say that despite being wounded in a first confrontation with police, Mr Jones was able to commandeer a police car and flee before being cornered and violently subdued.
The videotape, which has been shown repeatedly nation-wide has revived memories of the notorious police beating of Mr Rodney King which sparked off serious rioting in Los Angeles in 1991. Black leaders in Philadelphia, including the mayor, Mr John Street, have appealed for calm.
The Philadelphia Police Commissioner, Mr John Timoney, has said he is seriously concerned at the incident but rejected comparisons with the Los Angeles case. "For people to start making comparisons to Rodney King, I just think is outrageous," Mr Timoney, who was born in Dublin, told ABC's Good Morning America.
"He [Mr Jones] is resisting throughout. Now, does that justify the force? We won't know until we interview the officers," Mr Timoney said. He has promised a full investigation.
He was appointed head of the city's troubled police department over two years ago after resigning as deputy commissioner of the New York police department. His resignation was seen as a protest against the treatment by the mayor of New York, Mr Rudy Giuliani, of the then police commissioner, Mr William Bratton.
Mr Timoney, who was awarded a Medal of Valour while in New York, has also advised the Garda Siochana on anti-crime methods.
Ms Tracey Jones, the suspect's sister, said police overreacted: "They had already shot him five times. They didn't have to beat him."
The second car chase, after Mr Jones commandeered the police car, ended about a mile away when police surrounded the stolen vehicle. The beating was captured by the TV helicopter.
Ms Bertha Jones (40) was sitting on her porch when she saw the first confrontation. She said she saw the suspect jump over a gate with his hands in the air, as if to surrender.
"The cops ran over and started beating on him," she said. "They was beating on the man. He got one of their guns, started shooting, and by then I ran in the house.
"He fired his shots off. They fired. There was a whole lot of shooting going on," she said.
This latest accusation of police brutality comes at an embarrassing time for the City of Brotherly Love, which is preparing to welcome thousands of visitors and international media for the Republican Convention in two weeks' time.
The incident has also taken place while the National Association for the Advancement of Coloured People is holding its annual conference in Baltimore and discussing discrimination against minorities.
The mayor, Mr Street, cautioned against black people in Philadelphia jumping to conclusions on the basis of pictures of the arrest of Mr Jones. "As inflammatory as this tape might be, we have to keep in mind that the police were in the process of apprehending a criminal suspect who had resisted a number of attempts to arrest him and who had shot a police officer," he said.