Here's a timeline of major incidents since 2014 involving police officers which resulted in the deaths of black Americans.
17 July 2014: Eric Garner
Eric Garner died after he was wrestled to the ground by a New York police officer on suspicion of illegally selling cigarettes.
While in a choke hold, Mr Garner uttered the words "I can't breathe" 11 times.
The incident - filmed by a bystander - led to protests across the country. The police officer involved was later fired, but was never prosecuted.
It came a year after the Black Lives Matter movement emerged in response to the acquittal of the man who killed teenager Trayvon Martin in Florida.
9 August 2014: Michael Brown
Michael Brown, 18, was killed by a police officer, in Ferguson, Missouri, who was responding to reports that Brown had stolen a box of cigars.
The officer, Darren Wilson, stopped his car in front of Brown.
Brown reached into the car and punched Wilson, and in the struggle that followed, he tried to grab the police officer's gun, according to a report by the Department of Justice (DOJ), which was based on forensic evidence and interviews with dozens of witnesses.
One shot was fired and Brown ran off, pursued by Wilson. When he turned back and moved towards Wilson, the fatal shots were fired, according to witnesses.
Although the police officer was cleared of wrongdoing, the DOJ report was scathing about systemic problems in the Ferguson police and racial disparities in the justice system.
The incident led to multiple waves of protests and civil unrest in Ferguson, boosting the Black Lives Matter movement further.
22 November 2014: Tamir Rice
Tamir Rice, a boy of 12, was shot dead in Cleveland, Ohio by a police officer after reports of a male who was "probably a juvenile" pointing a gun that was "probably fake" at passers by.
Police claimed that they told Rice to drop the weapon - but instead of dropping it he pointed it at police.
The police confirmed that the gun was a toy after Rice had been shot dead.
The police officer who fired the fatal shots was sacked three years later for lying on his job application form.
In December 2020, the Justice Department said it was closing its investigation into the case as there was not enough evidence to bring federal criminal charges.
4 April 2015: Walter Scott
Walter Scott was shot in the back five times by a white police officer, who was later fired and eventually sentenced to 20 years in prison.
Mr Scott had been pulled over for having a defective light on his car in North Charleston, South Carolina, and ran away from the police officer after a brief scuffle.
The killing sparked protests in North Charleston, with chants of "No justice, no peace".
5 July 2016: Alton Sterling
Alton Sterling's death led to days of protests in Baton Rouge, Louisiana. Mr Sterling was killed after police responded to reports of a disturbance outside a shop.
The incident was caught on mobile phone footage and spread online.
The two officers involved did not face criminal charges, but one was dismissed and the other suspended from the police.
6 July 2016: Philando Castile
Philando Castile was killed while out driving with his girlfriend in St Paul, Minnesota.
He was pulled over by the police during a routine check, and told them he was licensed to carry a weapon, and had one in his possession.
He was shot as he was reaching for his licence, according to his girlfriend.
She live-streamed the encounter on Facebook. The officer involved was cleared of murder charges.
18 March 2018: Stephon Clark
Stephon Clark died after being shot at least seven times in his grandmother's backyard in Sacramento, California, by police who were investigating a nearby break-in.
Only a mobile phone was found at the scene, and Mr Clark was unarmed.
The release of a police video of the incident sparked major protests in the city.
In March 2019, the authorities announced that the two officers involved would not face criminal prosecution as the officers had feared for their lives, believing Mr Clark had a gun.
13 March 2020: Breonna Taylor
Breonna Taylor, a 26-year-old emergency medical technician, was shot eight times when officers raided her apartment in Louisville, Kentucky.
Louisville police said they returned fire after one officer was shot at and wounded.
Breonna Taylor's family filed a lawsuit, and in September 2020 reached a settlement of $12m (£9.4m) with the city authorities.
The lawsuit stated that Ms Taylor's partner - who was with her at the time - had fired in self-defence because the police did not identify themselves, and he thought the apartment was being burgled.
A grand jury charged one police officer not with Ms Taylor's death, but with "wanton endangerment" for firing into a neighbouring apartment.
Three officers involved in the raid have now been dismissed from the police force.
25 May 2020: George Floyd
George Floyd died after being arrested in Minneapolis and held down by police officers, one of whom had his knee on Mr Floyd's neck for more than nine minutes.
He pleaded that he couldn't breathe, and after his death, protests broke out across the US, and there were demonstrations in other parts of the world.
Former police officer Derek Chauvin - who had knelt on Mr Floyd - was convicted on charges of second-degree murder, third-degree murder and manslaughter after a three-week trial.
Three other officers who were involved in the incident will be tried later this year accused of aiding and abetting Mr Chauvin.
11 April 2021: Daunte Wright
Daunte Wright was shot and killed in Brooklyn Center, just north of Minneapolis.
After being pulled over for a traffic violation, the police told Mr Wright he was being arrested for an outstanding warrant.
He broke free and tried to re-enter his car, at which point an officer is heard shouting "Taser" several times before firing a shot.
Local police said the killing appeared to be accidental, and the officer, Kim Potter, had meant to use her Taser and not her handgun.
The family has rejected that explanation, and protests over the shooting have continued.
Mrs Potter has resigned from the police, and been charged with second-degree manslaughter.