More than a dozen people have been arrested and more than 30 officers were injured in protests stemming from the fatal police shooting of a black man in Philadelphia.
Officers said the man refused their orders to drop a knife in a confrontation captured on video.
The man, identified by city officials as Walter Wallace, 27, was shot before 4pm on Monday (8pm GMT) in an episode filmed by a bystander and posted on social media.
Witnesses complained that police had fired an excessive number of shots.
Mr Wallace’s father, Walter Wallace Sr, told The Philadelphia Inquirer that his son appeared to have been shot 10 times.
He said his son was also a father, was on medication and had struggled with his mental health.
“Why didn’t they use a Taser?” he asked.
Officers had been called to the predominantly black Cobbs Creek neighbourhood in west Philadelphia on reports of a man with a weapon, said Tanya Little, a police spokeswoman.
Police said they found Mr Wallace holding a knife and ordered him to drop the weapon several times. Wallace advanced toward the officers, who fired several times, Ms Little said.
In the video, a woman and at least one man follow Mr Wallace, trying to get him to listen to officers, as he briskly walks across the street and between cars.
The woman, identified by family members as Mr Wallace’s mother, screams and throws something at an officer after her son is shot and falls to the ground.
The video does not make it clear whether he was in fact holding a knife, but witnesses said he was.
Mr Wallace was hit in the shoulder and chest, Ms Little said, but she would not say how many times he was shot or the number of times officers fired.
One of the officers drove him to a hospital, where he was pronounced dead a short time later, she said.
No officers or bystanders were injured in the initial confrontation, Ms Little said. The names of the officers who fired the shots, and their races, were not immediately disclosed. Both were wearing body cameras and were taken off street duty pending the investigation.
Neighbours and witnesses soon gathered on Monday night on the block of Locust Street where the shooting occurred, with many saying that police did not have to shoot Wallace.
Police Commissioner Danielle Outlaw went to the scene and spoke to neighbours, and both Mayor Jim Kenney, a Democrat, and Ms Outlaw said they would hold a meeting soon to talk with the community about the shooting and other concerns.
“I heard and felt the anger of the community,” Ms Outlaw said in a statement, adding that the video “raises many questions” and that “those questions will be fully addressed by the investigation”.
Hundreds of people later took to the streets in west Philadelphia into the early hours of Tuesday, with interactions between protesters and police turning violent at times, the Inquirer reported.
Police cars and skips were set on fire as police struggled to contain the crowds. More than a dozen officers, many with batons in hand, formed a line as they ran down 52nd Street.
After this, the crowd largely dispersed.
Thirty officers were injured, most of them from thrown objects such as bricks and rocks, according to police.
One officer had a broken leg and other injuries after she was struck by a pickup truck, police said. The other injured officers were treated and released.
The 52nd Street corridor was also the site of protests against police brutality at the end of May, after George Floyd was killed by Minneapolis police.
Those protests have been the subject of City Council hearings, with protesters describing harsh and unnecessary tactics, including tear gas and projectiles fired by police.