Cleveland police are looking for a man who broadcast the fatal shooting of a stranger on Facebook.
The suspect, Steve Stephens, later said in a different video post that he had killed 13 people and wanted to kill more.
Cleveland police chief Calvin Williams confirmed one person had been killed, but said police did not know of any other victims.
Mr Williams added that "multiple forces" were looking for Mr Stephens, who "needs to turn himself in".
The victim was identified as 74-year-old Robert Goodwin.
Mr Williams said at a news conference on Sunday: "There is no need for any further bloodshed in this incident tonight. We need to bring this to a conclusion today. We need to get Steve from the streets."
Mr Stephens has been described as a 6ft 1in tall black male of medium complexion, driving a white or cream-coloured SUV.
The department has issued a photo of the suspect's vehicle and temporary tag number.
Facebook said the video was posted after the killing but was not broadcast on Facebook Live as police initially indicated.
The suspect did go live on the social media site at another point on Sunday.
The video of the killing was on Facebook for about three hours before it was taken down. Stephens's Facebook page was also eventually removed.
"This is a horrific crime and we do not allow this kind of content on Facebook," the company said.
"We work hard to keep a safe environment on Facebook, and are in touch with law enforcement in emergencies when there are direct threats to physical safety."
Victim Mr Godwin was apparently shot while out picking up cans in a plastic shopping bag, his daughter said.
"Not because he needed the money, it was just something he did," Debbie Godwin, 52, said. "That's all he was doing. He wasn't harming anyone."
She said her father, who had 10 children, was a gentle man.
"We called him the junk man," she said. "He'd pick up things off the street and fix them. He picked up bikes and he fixed them."
The motive for the shooting was not entirely clear from the shaky video, in which Stephens told Mr Godwin a woman's name and said: "She's the reason that this is about to happen to you."
Mr Godwin did not seem to recognise the woman's name.
The suspect then pointed a gun at Mr Godwin, who shielded his face with the plastic bag.