Graphic footage apparently showing two white police officers holding down and shooting dead a black man during an incident outside a convenience store in Louisiana has emerged.
Officers arrived at the Baton Rouge store at about 12:35am on Tuesday after an anonymous caller complained a man selling music CDs and wearing a red shirt threatened him with a gun, Cpl. L'Jean McKneely said.
The two officers who responded became engaged in an altercation with Alton Sterling, with one fatally shooting him, McKneely said.
Both officers have been placed on administrative leave, which is standard department policy, he said.
In the mobile phone footage of the altercation, a voice is heard shouting: "He's got a gun. Gun." Then shots ring out and the camera moves away.
Someone - apparently a bystander - can be heard saying "Oh my God", followed by another asking, "They shot him?" She replies: "Yes."
An autopsy shows Sterling, 37, of Baton Rouge, died on Tuesday of multiple gunshot wounds to the chest and back.
His death prompted a protest later in the day.
The store's owner, Abdul Muflahi, told WAFB-TV that the first officer used a stun gun on Sterling and the second officer tackled the man. Muflahi said as Sterling fought to get the officer off of him, the first officer shot him "four to six times."
The owner said Sterling, a father-of-five, did not have a gun in his hand at the time but he saw officers remove a gun from Sterling's pocket after the shooting.
McKneely said he could not confirm Muflahi's description of the event or any other details of the investigation.
The Advocate reported a crowd of people protesting the shooting gathered later on Tuesday afternoon at the store where it took place.
The group grew to over 200 people, who chanted "black lives matter" and "hands up don't shoot" and waved signs late into the night, according to the newspaper.