A Dekalb County Police officer has shot dead a naked black man who was apparently unarmed outside an apartment complex in Atlanta, police have said.
The officer had responded to a report of a man "knocking on doors, and crawling around on the ground naked" on Monday, county police chief Cedric Alexander has said.
The officer, who was white, met the man in the parking lot of the apartment block, Alexander said speaking at a press conference published online by broadcaster Fox5.
The county police chief said the man ran at the officer, who ordered him to stop before shooting him twice. He said officers did not find a weapon at the scene.
The officer, who had been with the department for seven years, was armed with a taser at the time of the shooting, Alexander said. The Georgia Bureau of Investigation is now to investigate the incident.
County police chief Alexander said he could "reasonably assume" the man shot on Monday was possibly suffering from a mental illness.
He declined to identify the man, but the New York Times has reported he was 27-year-old Anthony Hill.
The incident has sparked a reaction from a number of Twitter users, using the hashtag #blacklivesmatter and #AnthonyHill.
The shooting on Monday comes in the wake of a number of police killings of unarmed black men in the US.
Nationwide protests were sparked last year following incidents in Ferguson, Missouri and New York City.
According to the Reuters news agency, it is at least the third time an African-American man has been shot dead by police since last Friday, who either was or seemed unarmed.
Late last year, Dekalb County police faced protests after an officer shot dead a black man who had called 911 when his girlfriend was stabbed by an attacker in his apartment, local media has reported.
On Friday, police near Denver shot dead an unarmed man who was a wanted fugitive.
On the same day, an officer in Madison, Wisconsin, shot dead an unarmed 19-year-old. The shooting sparked protests in the city, with demonstrators chanting "black lives matter" on the streets and conducting a sit-in at the City Hall.