Matthew Dolloff, 30, was booked into jail for investigation of first-degree murder following the clash on Saturday afternoon in Denver’s Civic Centre 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 US Navy veteran who operated a hat-making business in the 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 Mr Keltner — participating in what was billed as a Patriot Rally, slapped and sprayed Mace at a man who appeared to be Mr Dolloff, the Post reported, based on its photographs from the scene.
The man identified by the newspaper as Mr 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 Mr 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 on Sunday that the arrest affidavit in the case remained sealed and referred further questions to the police.
