Police in California say they shot dead a Ugandan refugee when he pulled an object that turned out to be an e-cigarette from his pocket and pointed it at a police officer.
Dozens of demonstrators have taken to the streets of El Cajon, a suburb of San Diego, in protest at the killing of Alfred Okwera Olango, who was 38.
Mr Olango was killed on Tuesday after officers responded to a call from his sister who said that he needed help.
She said he was mentally unwell.
El Cajon police chief Jeff Davis said Mr Olango died after one officer fired an electronic stun gun and another officer simultaneously fired his firearm several times.
Police, who had already acknowledged that the object was not a weapon, confirmed on Wednesday that the object was a three inches (7.6cm) long silver vaping cigarette.
Christopher Rice-Wilson of the civil rights group Alliance San Diego questioned why one of the officers felt non-lethal force was appropriate while the other did not.
In El Cajon on Wednesday, protesters blocked streets. Outside the police station they chanted "murder, murder". One banner read "no killer cops".
"That could be my little brother," campaigner Mallory Webb told the crowd.
"I don't know what to do," she added. "I'm scared to walk the streets every single day."
Agnes Hassan said she knew Mr Olango, whom she described as well-educated but mentally ill. Ms Hassan said she had spent time with him in a refugee camp en route to the United States.
El Cajon is a suburb of San Diego with a population of around 100,000 people, including a sizeable number of refugees, many of whom fled the wars in Iraq and Syria.
Police said the shooting happened outside a row of shops as they responded to a report of a mentally unstable person walking in and out of traffic.
The call was apparently made by the victim's sister who said he was "not acting like himself".
El Cajon police department spokesman Lt. Rob Ransweiler said two officers arrived at the scene at about 14:10 (21:10 GMT) on Tuesday and the shooting happened one minute later.
The department says the officers were confronted by a man who refused to comply with instructions to remove a hand from his pocket, paced back and forth, then rapidly drew an object from the pocket, placed both hands together and extended them in a "shooting stance".
When detectives arrived, police say a witness voluntarily provided a mobile phone video of the incident. Authorities released a single frame from it appearing to show the "shooting stance" but did not release the video itself.
'I just called for help and you killed him'
Body cameras are on order for officers in El Cajon but have not yet arrived.
Another video posted on the internet which showed the aftermath of the shooting appeared to corroborate the police's account that they had ordered the man to remove his hand from his pocket.
"When he lifted his hand out ... he did have something in his hand but it wasn't no gun, and that's when they shot him," said a woman on the video.
Another woman, who identified herself as the victim's sister, shrieked and cried, telling officers that she had called them to help her brother.
"I just called for help and you came and killed him,'' she said.
Claims that Mr Olango had his hands in the air when he was shot have been disputed by the police.
This latest fatal shooting of a black man by police comes in a year when police violence against African Americans has divided the country and sparked numerous protests, some of which have turned violent, most recently in Charlotte, North Carolina.
Chief Davis has appealed for calm and is promising a thorough investigation into the shooting.
"This will be transparent,'' he insisted. "This will be looked at by multiple sets of eyes, and not just ours.''
As candles and flowers were laid at the scene of the shooting on Wednesday, Mr Olango's cousin Anthony Williams paid tribute.
"He was a cool dude, for real. He was no mean person, the whole picture how they got showing him pointing a gun, I don't believe none of that. That ain't him, I know for sure."