DENVER — A private security guard working for a Denver TV station is behind bars and accused in the deadly shooting of another man during dueling right- and left-wing protests, police said Sunday.

Matthew Dolloff, 30, was booked into jail for investigation of first-degree murder following the clash Saturday afternoon in Civic Center Park. 

Authorities have not identified the man killed, but his son told the Denver Post it was his father, Lee Keltner, a 49-year-old U.S. Navy veteran who operated a hat-making business in the Denver area.

"He wasn't a part of any group," Johnathon Keltner told the newspaper. "He was there to rally for the police department and he'd been down there before rallying for the police department."

A man — appearing to be Keltner — participating in what was billed a "Patriot Rally" slapped and sprayed Mace at a man who appeared to be Dolloff, the Post reported, based on its photographs from the scene. The man identified by the newspaper as Dolloff drew a gun from his waistband and shot the other person, according to the Denver Post journalist who witnessed the episode.

A woman who said she was Keltner's mother, Carol Keltner, wrote in a social media post that her son was killed after being shot in the head.

A decision on any charges will be up to the Denver District Attorney's Office, police said. A spokesperson for District Attorney Beth McCann said Sunday that the arrest affidavit in the case remained sealed and referred further questions to the police.

It was not immediately clear if Dolloff had an attorney who could comment on his behalf.

Police Division Chief Joe Montoya said two guns were found at the scene, as well as a Mace can.

The shooting occurred beneath a city surveillance camera, and police said they have footage of the incident, KUSA-TV reported.

KUSA said it had hired the guard through the Pinkerton security firm. 

"It has been the practice of 9NEWS for a number of months to hire private security to accompany staff at protests," the station said.

The right-wing "Patriot Rally" was one of two demonstrations happening at about the same time that drew hundreds of people to the park. Protesters at a left-wing "BLM-Antifa Soup Drive" nearby held up flags and signs railing against Nazis and white supremacists.

Security guards in Denver are supposed to be licensed, with additional endorsements needed to carry a firearm or operate in plainclothes, according to rules for the industry adopted by the city in 2018.

In photos from Saturday's shooting, Dolloff did not appear to be in uniform. His name does not show up on a city-run database that lists several thousand licensed security guards.

Representatives of Pinkerton did not immediately return email and telephone messages for comment.