A day of peaceful remembrance marking the anniversary of a black teen's killing by police in the US city of Ferguson came to a violent end Sunday as gunfire left at least one protester injured.
St. Louis County police said an officer had opened fire after coming under "heavy gunfire," and pictures on Twitter showed at least two cars with bullet holes.
Local media reported that one person had been taken to the hospital.
Demonstrators had taken to the streets to mark the anniversary of 18-year-old Michael Brown's death in a fateful encounter on August 9, 2014 with officer Darren Wilson.
The 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. At least one shop was looted in the hours ahead of the gunfire, which occurred shortly after 11:00 pm (0400 GMT).
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 gathered in Brooklyn earlier, 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.
The 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 terms of legislative action, 40 legislators have taken up some measure of holding police departments accountable but only a tiny fraction of which actually moved towards holding police departments accountable," said NAACP president Cornell William Brooks in an interview with CBS's Face the Nation.
He urged passage of laws against racial profiling by police and support for reforms requiring body cameras, independent prosecutors and retraining of US police departments.
Erica Snipes, the daughter of Eric Garner, who died after being held in a choke hold by police in New York, also appealed for reform.
"This year has just been so hard. No accountability, no justice. Police are still killing us -- it's a crisis that's going on," she said at the rally in Ferguson.
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.
"I feel a great urgency to get as much done as possible," he said in an interview with NPR, parts of which were released Sunday.
"And, 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. 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.
On Saturday, protesters in Ferguson had marched along one of the avenues hit by fierce rioting last November when a court decided not to indict Wilson.
The peaceful march, led by Brown's father, saw participants shout slogans such as "Hands up, don't shoot" and "We do this for who? We do this for Mike Brown."