There was vandalism after thousands of people attended a vigil for an unarmed black US teenager who was shot and killed by a police officer.
Several car windows were smashed and stores were looted as people carried away armloads of goods after the event in a suburban St Louis street.
The candlelight gathering was for Michael Brown, 18, who police said was shot multiple times on Saturday after a scuffle involving the officer and two people in Ferguson, a predominantly black suburb of the city.
At the vigil, people placed candles, flowers and a teddy bear at the location where Mr Brown was killed. One group broke off to spray paint "R.I.P. Michael" on the street.
Afterwards, some people were seen looting a convenience store.
Several other shops along a main road near the shooting scene were broken into and looted, including a cheque-cashing store, a boutique and a small grocery store.
People were seen carrying armloads of goods such as bags of food and toilet paper.
TV footage showed streams of people walking out of a shop carrying bottles of alcohol, and in some cases protesters were standing on top police cars or taunting officers in riot gear.
Other witnesses reported seeing people vandalise police cars and kick in windows. Television footage showed windows broken in a TV station van.
"Right now, the small group of people are creating a huge mess," Ferguson's mayor, James Knowles, told St. Louis KTVI-TV.
"Contributing to the unrest that is going on is not going to help. ... We're only hurting ourselves, only hurting our community, hurting our neighbours. There's nothing productive from this."
He said he understood that people wanted to vent their frustrations as the investigation into Mr Brown's death progresses.
"We're going to obviously try to urge calm," he said.
St. Louis County Executive Charlie Dooley said there were no reports of injuries but confirmed widespread property damage. "Right now I'm just worried about people, not property," he said.
County Police Chief Jon Belmar had said the shooting occurred after an officer encountered two people - one of whom was Mr Brown - on the street near an apartment complex in Ferguson.
He said one of the men pushed the officer back into his squad car and a struggle began. At least one shot was fired from the officer's gun inside the police car.
Mr Belmar said the exact number of shots was not known, but "it was more than just a couple".
He also said all shell casings found at the scene matched the officer's gun. Police are still investigating why the officer shot Mr Brown, who police have confirmed was unarmed.
Ferguson Police Chief Tom Jackson said authorities were still sorting out what happened inside the police car. It was not clear if Mr Brown was the man who struggled with the officer.
The struggle spilled out into the street, where Mr Brown was shot multiple times.
Mr Jackson said the second person has not been arrested or charged. They are not sure if that person was unarmed.
Mr Brown's mother, Lesley McSpadden, said he had graduated from high school and was about to enter a local college.
She said she does not understand why police did not subdue her son with a club or Taser, and she said the officer involved should be fired and prosecuted.
"I would like to see him go to jail with the death penalty," she said at the site of the shooting, fighting back tears.
The teenager's father, Michael Brown Sr had said at the vigil that he appreciated the outpouring of support.
The Rev Al Sharpton called the shooting "very disturbing" and said he planned to go to Ferguson to meet the family.