The mayor of Berkeley has said the shooting of an 18-year-old black man by police late last night is not the same as the Michael Brown case.
The man, who has been named as Antonio Martin, was shot at a petrol station in a St Louis suburb near where unarmed teen Michael Brown was killed by a white officer in August.
Mayor Theodore Hoskins has said he does not want to jump to conclusions while local and county officials investigated the shooting, but he also emphasised what he said were clear differences with the Michael Brown case.
"We have a majority of black officers in our city," Mayor Hoskins said, drawing contrasts with Ferguson.
"The mayor is black. The city manager is black. The finance director is black. The police chief is black. Our police officers are more sensitive."
The scene of last night’s shooting has been cordoned off with yellow tape and guarded by police, some in helmets and carrying riot shields, with bystanders shouting at them in a tense standoff.
A crowd of 200 to 300 people gathered at the petrol station after the shooting, and bricks and three fireworks were thrown, two of them at the police officers at the scene, St Louis County Police Chief Jon Belmar said.
Around 50 officers attended the scene.
Two officers were injured and four people were arrested for assault before calm was restored, Mr Belmar said.
Images and video footage showed a flash, a loud bang and smoke filling an area near the petrol pumps, but it was not clear whether they were caused by bystanders or the police
The shooting occurred three days after the worst fears of police-reform activists and the direst warnings of police leaders came to pass: on Saturday afternoon, a man summarily shot dead two officers in their patrol car in New York City, targeting them only because of the uniform they were wearing.
Police in Berkeley said the man who was killed had pointed a handgun at an officer who was conducting a "routine business check".
The officer had approached two men outside the petrol station after 11pm (5am Irish time) in the suburb of Berkeley.
"Fearing for his life, the Berkeley Officer fired several shots, striking the subject, fatally wounding him," St Louis County Police Department spokesman Brian Schellman said in a statement.
The second man fled the scene.
St Louis County police said they recovered the deceased's man's handgun at the scene.
The St Louis Post-Dispatch quoted the deceased 18-year-old’s mother as having said the teenager was with his girlfriend at the time of the shooting.
"They won't tell me nothing. His girlfriend told me that the police was messing with him," the man's mother, Toni Martin, told a local broadcaster.
"When he was trying to get up and run, they start shooting."
Berkeley lies beside the suburb of Ferguson, where police officer Darren Wilson shot Michael Brown on 9 August, a killing that fuelled criticism of the way police and the criminal justice system treat minority groups.
Protests in Ferguson have taken place for months and spilled over into violence when a grand jury decided not to charge Officer Wilson.
Demonstrations in cities across the country gained in momentum when a New York grand jury decided not to charge police over the death of Eric Garner, a 43-year-old black man whom police tackled and put in a chokehold.
Before the latest incident, about 200 people marched in New York yesterday, defying Mayor Bill de Blasio's call for protests to be suspended after two police officers were killed in their patrol car on Saturday in an apparent revenge attack.
In Los Angeles, police said they would investigate whether any officers were involved in the singing of a song, at a party organised by a retired policeman,that poked fun at the Ferguson killing.
The lyrics of the song, on a video posted on entertainment news website TMZ, said: "Michael Brown learned a lesson about amessin' with a badass policeman."
