A US mayor is pressing for calm in his St Louis suburb after a white police officer fatally shot a black 18-year-old who police say pointed a handgun at the officer.
St Louis County police identified the young man killed during the Berkeley encounter as Antonio Martin.
County Police chief Jon Belmar said the officer was questioning the 18-year-old and another man about a theft at a convenience store when the young man pulled a handgun.
Mr Belmar said the officer fired three shots, one striking the 18-year-old.
Berkeley is near Ferguson, where the fatal shooting of Michael Brown by a white police officer sparked sometimes violent demonstrations.
Berkeley mayor Theodore Hoskins said the Martin and Brown cases are different, partly because there was no video of the fatal encounter in Ferguson.
The 34-year-old, white Berkeley police officer, who has been on the police force for six years in the 25,000-resident suburb, is on administrative leave pending an investigation, Mr Belmar said.
S t Louis County police and the city of Berkeley are investigating, Mr Hoskins said.
"He will carry the weight of this for the rest of his life, certainly for the rest of his career," Mr Belmar said of the officer whose name was not immediately released. "There are no winners here."
The officer was not wearing his body camera, and his police cruiser's dashboard camera was not activated because the car's emergency lights were not on, Mr Belmar said.
Police released surveillance video from the car park outside the store. The nearly two-minute clip shows two young men leaving the store as a patrol car rolls up, and the officer gets out and speaks with them.
About 90 seconds later, the video appears to show one of the men raising his arm, though what he is holding is difficult to see because they were several feet from the camera. Mr Belmar said it was a 9mm handgun - loaded with one round in the chamber and five more in the magazine.
Police were searching for the other man, who fled on foot.
It was the third fatal shooting of a black suspect by a white police officer in the St Louis area since Brown was killed. Kajieme Powell, 25, was killed on August 19 after approaching St Louis officers with a knife. Vonderrit Myers Jr, 18, was fatally shot on October 8 after allegedly shooting at a St Louis officer.
Each shooting has been met by protests, and a crowd quickly gathered in Berkeley. The demonstration involving about 300 people turned violent.
More than 50 police officers, some in riot gear, responded. Video showed some wrestling with protesters. Mr Belmar said officers used pepper spray but not tear gas. Four people were arrested on charges of assaulting officers.
Mr Belmar said three explosive devices, perhaps fireworks, were tossed near petrol pumps, and some protesters threw rocks and bricks. One officer hit by a brick was treated for facial cuts, and another was treated for a leg injury sustained as he retreated from an explosive.
"I understand police officers have a job and have an obligation to go home to their families at the end of the night," said 36-year-old Orlando Brown, one of the protesters. "But do you have to treat every situation with lethal force? ... It's not a racial issue, or black or white. It's wrong or right."