DENVER (AP) — Denver officials were investigating Monday how an armed security guard for a television station who is suspected of fatally shooting a man following an altercation following opposing protests was able to work in the city without a license.

Matthew Dolloff, 30, was being held in jail for investigation of first-degree murder following Saturday afternoon's shooting near Civic Center Park as protesters filed out of the park following the demonstrations — a “Patriot Muster” and a “BLM-Antifa Soup Drive” counterprotest. He has not been charged and no lawyer was listed as representing him in court records.

Under rules adopted by Denver in 2018, both security companies and the guards they employ must have city licenses. Guards must undergo 16 hours of training and an FBI background check to get a license and complete eight hours more training to renew their license each year, said Eric Escudero, a spokesman for the city’s Excise and Licenses Department. Guards that carry firearms must also be screened by police, he said.

Dolloff did not have a license at the time of the shooting and there is no record of him applying for one, Escudero said. Companies that employ guards without licenses can have their licenses suspended or revoked and face fines. Individual guards who do not have licenses can be punished with a $999 fine and up to one year in jail.

Dolloff did have a permit to carry a concealed weapon in Colorado issued by his local sheriff’s office but it was suspended Monday because of the allegations against him. Elbert County Sheriff Tim Norton said he will decide whether Dolloff will get the five-year permit back based on what happens in the criminal case.

According to state business records, Dolloff was listed as the registered agent for a farm that raises animals including turkeys, sheep and goats in Elizabeth, a town just beyond the Denver metro area. No one answered the phone at the farm on Monday and a message left for another person listed in business filings was not returned.

KUSA-TV said Sunday that it has been hiring private security to accompany its staff at protests for a number of months. It said Dolloff had been hired through the Pinkerton security company. However, in a statement, Pinkerton said Dolloff was a contractor, not a Pinkerton employee. The company did not reveal the name of the contract company Dolloff worked for.

“Pinkerton is fully cooperating with law enforcement authorities in their investigation of this matter,” it said.

Authorities have not identified the man who was 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 said of his father. “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 — slapped and sprayed Mace at a man who appeared to be Dolloff, the Post reported, based on its photographs from the scene.

Carol Keltner, who said she was the victim's mother, wrote in a social media post that her son was shot in the head.

Police have said two guns and a Mace can were found at the crime scene.

Police declined on Monday to release any more details about what happened, including who the guns belonged too, because they do no want to harm their ongoing investigation, department spokesperson Jay Casillas said. The document laying out the reasons for Dolloff's arrest has been sealed.

An organizer of the patriot demonstration, John Tiegen, said on Instagram on Sunday that it was not clear if the man who was killed attended the demonstration or was just nearby but he extended his condolences to his family.

“It’s tragic that Americans find themselves in danger just by coming together and showing support for their country,” he said.

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The story has been corrected to say that the shooting happened near Civic Center Park, not in it.