Ferguson anniversary protest: Tyrone Harris in critical condition after shooting involving four plain-clothed police officers

Demonstrators had gathered to mark a year since Michael Brown died

A man who was injured during the shooting involving police (REUTERS/Rick Wilking)

A peaceful rally in Ferguson to mark the first anniversary since a white police officer shot unarmed black teenager Michael Brown turned violent by nightfall, after three shootings broke out which left one man fighting for his life.

Footage from the scene of the shooting on West Florissant Avenue in the Missouri city at around 11pm, showed a young black man lying on the floor covered in blood, before he was rushed to hospital in an ambulance.

A young woman was seen crying and shouting that her brother had been shot, as another fainted.

The man's father has since named the victim as 18-year-old Tyrone Harris in an interview with the St Louis Post-Dispatch. He told the newspaper that his son had been "real close" to Brown.

Warning: some readers may find this footage distressing

Calling those involved "criminals not protesters", St Louis County's police chief Jon Belmar told a press conference that the man approached police as two approximately six-person-strong groups of people engaged in a gunfight. He did not named Harris as the victim.

The man, who is believed to have been armed, approached and shot at four plain-clothed officers in an unmarked car, prompting them to respond with gunfire from inside the vehicle, he said. The officers then pursued the man on foot.

The shooter then fired on officers again, and the four police officers shot back once again.

The man shot is currently in a "critical, unstable condition" in hospital where he is undergoing surgery, Belmar said. He added that a police officer was being treated for cuts to his face after he was hit with a brick.

It is unclear how many people have since been arrested, he added, and said a stolen 9mm gun was retrieved from the scene.

As the police officers involved were not in uniform, body cameras were not in use during the shooting, said Belmar, before he refused to disclose the race of the officers involved.

But Harris Senior told the St Louis Post that his family "think there's a lot more to this than what's being said."

Around two hours later, two further shootings broke out on Canfield Drive, a short walk from West Florissant Avenue, where smoke was used to disperse protesters, Belmar told reporters.

Following the initial shooting, the police released images of an unmarked car with gunshot holes in the front window.

Earlier in the day, Michael Brown Senior, the late teenager’s father, led a peaceful thousand-person-strong rally in the town which started at the spot where white police officer Darren Wilson shot his son on 9 August 2014. Months later, a grand jury and the US department of justice would decide not to prosecute Wilson and said he had acted lawfully. By November, Wilson announced his resignation.

Stopping during the march at a permanent memorial for his son, Brown said “Miss you”, after he thanked supporters for not allowing his son’s killing to be “swept under the carpet”.

As protesters observed four-and-a-half minutes silence marking the number of hours that Brown's body lay in the middle of the street, white doves were released.

But as darkness fell, the scene transformed and dozens of protesters blocked traffic and smashed store windows along West Florissant Avenue – where demonstrations erupted last year - as they chanted "Shut it down."

Riot police soon arrived on the scene in armed vehicles after shots rung out.

The teenager’s was one of many similar fatal police shootings of unarmed black men that have highlighted racial tensions in the US and sparked a nation-wide Black Lives Matter movement.

Additional reporting by AP and Reuters