Police in Missouri have released a video that appears to show a black teenager brandishing a gun before he was shot and badly wounded by officers.
Police said the short clip from a security camera showed Tyrone Harris, 18, grabbing a gun from his waistband.
Mr Harris’s father has said his son was unarmed and was running away from police when he was shot on Sunday.
Tyrone Harris was fired on during protests in Ferguson to mark a year since the killing of Michael Brown.
Vigilantes or peacekeepers? Ferguson’s “Oath Keepers”
According to police, a gunfight erupted between two rival groups in West Florissant Avenue and a suspect, identified as Tyrone Harris, then shot at plain-clothes police officers, who returned fire.
“The video shows Harris grab a handgun out of his waistband once shots are fired during the protest in the West Florissant corridor,” St Louis’s police department said.
But Mr Harris’s father said, before the video was released, that his son had been unarmed and was “running for his life”.
Prosecutors have filed 10 charges against Tyrone Harris, including assaulting an officer.
A state of emergency was declared on Monday as protests continued to mark the anniversary of the fatal shooting of unarmed black teenager Michael Brown by a white police officer.
Protesters staged a sit-in outside the main courthouse in St Louis and gathered along a major highway as part of a day of civil disobedience called by activists.
Police in riot gear forced people off the streets on Monday night. They said 23 people were reportedly detained, but “there were no shots fired, no smoke or tear gas used”.
The state of emergency was still in effect on Tuesday but no major protests were reported.
Michael Brown, 18, was shot dead in August 2014 by a white police officer who was later cleared of any wrongdoing by a grand jury and the US Department of Justice.
The death triggered a wave of protests over alleged racism and the use of excessive force by US police officers.
Ferguson resident Roberta Lynch, 51, said relations with police had not improved in the year since Michael Brown’s death.
“They are doing the same old stuff, taking our rights,” she said. “They need to give us our space.”
What happened in Ferguson in 2014?
There have been a number of high-profile shootings of unarmed black men in US cities in recent months.
On Friday, 19-year-old Christian Taylor was shot dead by a white police officer after he was spotted on surveillance footage vandalising cars in Arlington, Texas. The police officer has since been fired.
Campaigners were further incensed when a justice department investigation found widespread racial bias in the Ferguson police force.
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