A man has been arrested over a fatal shooting at rival protests in Denver, Colorado on Saturday.
Local police later identified the suspect as 30-year-old Matthew Dolloff, who is believed to be a security guard.
Reports said the dead man was taking part in the right-wing "Patriot Rally". Police said he was not linked to left-wing counter-protests.
A Denver TV station said it had hired the suspect to protect its crew, but police have not confirmed this.
The suspect is being held on suspicion of first-degree murder.
The "Patriot Rally" taking place in Denver was met by counter-protests by several groups who said they were holding a "Black Lives Matter-Antifa Soup Drive".
The shooting took place in a courtyard of the Denver Art Museum.
Photographs published by the Denver Post newspaper appear to show a confrontation during which the demonstrator strikes the security guard and sprays pepper spray at him before the security guard opens fire.
Denver Police Chief of Investigations Joe Montoya said the incident took place shortly after 15:30 local time (21:30 GMT). He said there had been a "verbal altercation" and a firearm was discharged.
Two guns were recovered at the scene and a suspect was taken into custody, he said.
Local TV station KUSA-TV said on its website that the arrested man was a security guard it had hired to protect its crew.
"It has been the practice of (KUSA) for a number of months to hire private security to accompany staff at protests," the station said.
However, Chief Montoya said he could not confirm that the suspect was working for the station. Neither he nor the victim have yet been identified by the authorities.
Chief Montoya said police had kept the rival rallies separate and there had been no other arrests.
What other protests are taking place?
In Milwaukee in the state of Wisconsin, protesters turned out for a fourth day after the district attorney said a black police officer would not face charges over the killing of an armed black teenager outside a mall earlier this year.
Earlier this week Milwaukee County District Attorney John Chisholm said Officer Joseph Mensah had been justified in firing because 17-year-old Alvin Cole had pointed a gun at police. It is the third deadly shooting Officer Mensah has been involved in in five years. He remains on administrative suspension.
Meanwhile, police in Portland, Oregon, made arrests at a protest against police violence outside a police station in the north of the city. A police spokesman said the force had believed the protesters were going to engage in "direct action".