The shooting of a black teenager sent hundreds of angry residents onto the streets of a US city in a confrontation with police that lasted several hours.
They shouted obscenities and some threats, such as "kill the police" but there were no reports of injuries during the incident in the predominantly black city of Ferguson, Missouri.
The teenager's grandmother, Desiree Harris, saw the 18-year-old running near her home on Tuesday afternoon when she passed him in her car. Minutes later, she found his body on the street - fatally shot by a police officer.
Ms Harris said she was expecting her grandson, Michael Brown, to visit her that afternoon and discovered him dead after she heard a commotion outside her apartment complex.
"He was running this way," she said. "When I got up there, my grandson was lying on the pavement. I asked the police what happened. They didn't tell me nothing."
The teenager's mother, Lesley McSpadden, told an acquaintance the shooting was "wrong and it was cold-hearted," the St Louis Post-Dispatch reported.
According to the newspaper, Mr Brown's stepfather, Louis Head, held a sign that read: "Ferguson police just executed my unarmed son!!!"
A spokesman with the St Louis County Police Department, which is investigating the shooting at the request of the local department, confirmed a Ferguson police officer shot the man. The spokesman did not give the reason for the shooting.
John Gaskin, a member of the St Louis County NAACP civil rights group, said the FBI should get involved "to protect the integrity of the investigation".
He said officials in the organisation spoke to St Louis County Police Chief Jon Belmar, who told them the teenager had been shot twice.
Mr Gaskin said the angry crowd was reacting to a "trauma".
"Any time you have this type of event that's taken place, emotions are going to run high," he said.
"But for 600 people to gather around an area to see where a man is lying in the street, that means something happened that should have not happened."
Last night, dozens of police cars remained parked near the shooting scene as mourners left votive candles, rose petals, a large stuffed animal and other remembrances at a makeshift memorial in the middle of the street.
At the height of the post-shooting tensions, police at the scene called for about 60 other police units to respond to the area in Ferguson, a city of about 21,000 residents, about two-thirds of whom are black.
Ms Harris said her grandson had recently left high school and was looking forward to the future, including possibly attending college.
"My grandson never even got into a fight," she said. "He was just looking forward to getting on with his life. He was on his way."
Ferguson Police Chief Thomas Jackson told the Post-Dispatch that the officer involved has been placed on paid administrative leave.
"We are hoping for calm and for people to give us a chance to conduct a thorough investigation," he said.