A state of emergency has been declared in the US city where an unarmed black teenager was shot by a white police officer a year ago.
An 18-year-old has been charged with an assault on officers after an exchange of gunfire during protests in Ferguson, Missouri last night.
Police now fear there could be more violence there tonight and have declared a state of emergency.
Authorities said the teen, Tyrone Harris, was wounded during a gun battle with plainclothes officers on the anniversary of Michael Brown Jr's death.
The 18-year-old allegedly opened fire on the officers, who had been tracking Harris in an unmarked van on Sunday night.
St Louis County prosecutors have charged Harris with four counts of assault on law enforcement and shooting at a motor vehicle.
The teen, who remains in critical condition in hospital, was ordered held on $250,000 bond.
St Louis County Police Chief Jon Belmar said the officers suspected Harris was armed and had been keeping an eye on him during the protests.
At one point, Harris alleged approached the police vehicle and opened fire, Chief Belmer said. The officers then returned fire and pursued the suspect on foot.
The St Louis County Police Department tweeted pictures of at least two unmarked cars that were hit by gunfire.
Video captured on a mobile phone showed officers standing over the injured suspect as an onlooker can be heard urging the officers to "please get him some help".
Earlier memorial in Ferguson
Earlier on Sunday, crowds marched to remember Michael, who was fatally shot by Ferguson officer Darren Wilson on August 9th last year.
His shooting added to the national Black Lives Matter movement and a debate on race and justice.
The protesters observed four-and-a-half minutes of silence at midday to represent the roughly four-and-a-half hours the 18-year-old's body lay in the middle of the street after he was shot.
Two doves were released before the crowd marched silently from the spot where the unarmed teenager was shot.
A service commemorating the anniversary was held at a church in the St Louis suburb.
The teenager's father Michael Brown Snr thanked supporters for not allowing his death to be "swept under the carpet".
He said: "You knew in your gut that (the shooting) wasn't right. And you knew what that officer did was unjustified."
Dozens of people gathered in New York's Union Square in a vigil for Mr Brown, calling for more demonstrations against police killings of minorities. Several people were arrested in Brooklyn at a symbolic "die-in" to protest against the shooting.
It comes after Mr Wilson gave an interview to the New Yorker, in which he said he does not spend much time thinking about the young man he killed in Ferguson.
The 29-year-old, who lives with his family in hiding, said: "Do I think about who he was as a person? Not really, because it doesn’t matter at this point".
"I only knew him for those 45 seconds in which he was trying to kill me, so I don’t know".
Police said Mr Brown stole items from a convenience store and shoved the owner. He was stopped by Mr Wilson nearby and a confrontation began inside his patrol car.
That spilled outside and the former officer claimed Mr Brown came at him menacingly and he fatally shot him.
Witnesses have claimed Mr Brown had his hands up in surrender when he was shot.
A grand jury and the US Department of Justice declined to prosecute Mr Wilson, who resigned as a police officer in November.
After three nights of protests, some organisers have vowed to stage a day of civil disobedience on Monday.
