St Louis police have shot dead a black teenager who they say pointed a gun at them, reigniting racial tensions first sparked by the killing of an unarmed black teen in another Missouri town a year ago.
St Louis Police Chief Sam Dotson said the shooting took place when young black men ran out the back door of a house where officers were carrying out a search warrant.
Officers ordered two youths to stop in an alley behind the house. One suspect pointed a gun at officers who then fired four times, killing him, Chief Dotson said.
"Detectives were looking for guns, looking for violent felons, looking for people that have been committing crimes in the neighbourhood," he said.
Police identified the suspect as 18-year-old Mansur Ball-Bey. The second youth fled.
Crowds gathered at a nearby intersection shortly after the shooting and then again in the evening.
Chief Dotson said at a press conference some protesters threw bricks and glass bottles at officers, who used shields to protect themselves and then tear gas to disperse the crowd.
A car was set on fire and some local businesses had reported robbery attempts, he said.
Nine people were arrested on charges of impeding traffic and resisting arrest, police said.
Chief Dotson told reporters Mr Ball-Bey's gun was one of three stolen firearms recovered from the scene and said officers also recovered crack cocaine.
St Louis police said the officers involved in the shooting were white, aged 33 and 29, each with about seven years on the force. They are on administrative leave.
The shooting came ten days after St Louis was flooded with protesters marking the anniversary of the killing of unarmed black teenager Michael Brown by a white police officer on 9 August last year in Ferguson, not far from St Louis.
Mr Brown's death sparked a nationwide movement against what protesters say is police violence against minorities.
Yesterday's shooting also came as activists were in the area to mark the anniversary of the police shooting of another black man in St Louis, Kajieme Powell.
Police say officers shot Mr Powell when he approached them with a knife.
