Several hundred people have paused in silence in the US town of Ferguson on the first anniversary of the killing of unarmed black teenager Michael Brown.
The four-and-a-half-minute tribute was meant to reflect the approximate hours that Mr Brown's body lay in the street. A march was also held.
The shooting of the 18-year-old by white police officer Darren Wilson sparked demonstrations across America.
It fuelled a national protest movement against racial bias by the police.
Activists and religious figures from across the country were among those who have gathered this weekend in Ferguson, a suburb of St Louis, Missouri.
The Reverend Osagyefo Sekou, from the Ferguson Action Council, told the BBC that last year's events had led to some positive change in the black community but not in society at large.
"We have not seen the kind of systematic change that is necessary, whereby every other day in America a mother is not writing the eulogy of her child which shall be the elegy of the nation," he said.
Those who gathered at the spot in the St Louis suburb where Michael Brown was fatally shot on 9 August 2014 saw two white doves released.
Speaking after the moment's silence, Michael Brown's father thanked supporters for not allowing what happened to his son to be "swept under the carpet".
He then led a march to a Ferguson church, pausing along the route at a permanent memorial for his son, where he said: "Miss you."
In the borough of Brooklyn in New York, protesters lay on the ground for four-and-a-half minutes to mark Michael Brown's death. A rally was expected later in central Manhattan.
The protests, which sometimes involved violent clashes between demonstrators and police, continued in Ferguson for weeks after the killing.
The protest movement gained fresh impetus in November, when a grand jury decided not to charge Mr Wilson.
A year after Ferguson, there is more we must all do to address systemic racism and ensure every American feels safe in their community. -H— Hillary Clinton (@HillaryClinton) August 9, 2015
Mr Wilson, who argued that he was acting in self-defence, resigned from the police force in November.
In March, a justice department investigation found evidence of widespread racial bias in the Ferguson police department.
The report led to several high profile resignations, including the chief of police.
The "Black Lives Matter" movement that emerged in the wake of Mr Brown's death has focused attention on the troubled relationship between black communities and police forces in a number of US states.
Another police shooting of an unarmed black man took place on Friday.
College football player Christian Taylor, 19, was shot dead after police were called to a possible burglary at a car dealership in Arlington, Texas.
Officer Brad Miller, who had never before fired his weapon in the line of duty, has been placed on administrative leave.