FERGUSON, United States - Police shot and critically wounded a man who opened fire at them in the US city of Ferguson on Sunday, ending what had been a day of remembrance for a black teen killed a year earlier.
The violence came after hundreds of peaceful protesters took to the streets of the St. Louis suburb to mark one year since a white Ferguson officer fatally shot 18-year-old Michael Brown, in an incident that sparked widespread unrest and highlighted persistent racial tensions in America.
The latest shooting came after two rival groups exchanged gunfire in the late evening, police said.
One man who ran from the scene encountered four plain-clothes detectives in a van, opening fire at them and striking their vehicle, St Louis County Police Chief Jon Belmar told reporters.
The police returned fire, then pursued the man on foot and opened fire again, he said.
"All four fired at the suspect and the suspect fell," Belmar said, adding that the man was in "critical, unstable condition" and in surgery.
Video captured by AFP showed a black man lying facedown on the ground in handcuffs, bleeding profusely. Belmar declined to comment on the race of the detectives.
He said there was "a remarkable amount of gunfire", with as many as 50 bullets let loose in the initial shooting between the two groups.
The detectives involved had from six to 12 years of experience and were placed on administrative leave.
Belmar said those who had started the shooting were not protesters but "criminals".
"There is a small group of people out there that are intent on making sure that we don't have peace that prevails," he said.
Demonstrators had taken to the streets to mark the anniversary of Brown's death in a fateful encounter on August 9, 2014 with officer Darren Wilson.
That shooting - and a subsequent decision not to indict Wilson - led to violent unrest and set off nationwide protests and intense scrutiny of heavy-handed police tactics in a series of cases that ended in the deaths of unarmed blacks.
Sunday's day of remembrance had been peaceful until a handful of protesters grew rowdy later in the evening. Two businesses were looted in the hours ahead of the gunfire, which occurred shortly after 11:00 pm (0400 GMT).
Vigil in New York
A crowd of about 300 people had gathered earlier to mark the anniversary, during which they observed four and a half minutes of silence and released two white doves.
The time represented the four and a half hours that Brown's body lay face down in the street before being taken away.
Many in the crowd wore T-shirts emblazoned with Brown's portrait and the words "Choose Change". Others carried signs, including one that read: "STOP killing black children." Brown's father, also called Michael, said he was grateful so many people had turned out for the march.
"If it wasn't for y'all this would be swept under the carpet. So I just want to give my love out to y'all," he said to the crowd.
In New York, dozens of people gathered at Union Square to hold a vigil for Brown in solidarity with Ferguson and to call for ongoing demonstrations against police killings of minorities.
About 100 people had gathered earlier in Brooklyn, staging a symbolic "die-in" to protest Brown's shooting. Police arrested several people.
One year on, black leaders say they have witnessed a dramatic change in American attitudes toward race, but see little action by lawmakers to enact policing reforms.
Yet another high-profile shooting occurred Friday, when a Texas police officer fatally shot 19-year-old unarmed college football player Christian Taylor after he drove his vehicle through the front of a car dealership.
Cornell William Brooks, head of the National Association for the Advancement of Colored People, one of the country's oldest civil rights group, called the pace of legislative change "glacial".
In an interview with CBS's Face the Nation, he urged the passage of laws against racial profiling by police and support for reforms requiring body cameras, independent prosecutors and retraining of US police departments.
President Barack Obama meanwhile dismissed criticism that he had been too reluctant to tackle issues of race early in his tenure as America's first African-American president.
"There's no doubt that after over six and a half years on this job, I probably have an easier time juggling a lot of different issues," he said in an interview with NPR.
"And, it may be that my passions show a little bit more. Just because I have been around this track now for a while." Outrage over the police killings of Brown and other black Americans in the past year has been channeled into a sustained nationwide movement with the social media hashtag #Blacklivesmatter becoming its rallying cry.