Updated

One person was shot and killed, and a local news station's private security guard was in custody Saturday evening after protests between opposing groups turned violent in Denver's Civic Center Park, city police said. 

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The man who was shot was part of a pro-police "Patriot Rally," according to a report.

"Further investigation has determined the suspect is a private security guard with no affiliation with Antifa," the Denver Police Department wrote in a Twitter message.

Matthew Dolloff Courtesy Denver Police/ Twitter

KUSA-TV, a local Denver news station also known as 9NEWS, reported that a suspect in police custody was a private security guard hired by the station. 

"The private security guard was contracted through Pinkerton by 9NEWS," the news outlet wrote. "It has been the practice of 9NEWS for a number of months to hire private security to accompany staff at protests."

A KUSA producer also was initially in custody, but has since been released. 

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Video of the incident shows one shot being fired. Denver police then quickly cordon off the scene, giving medical aid to the victim and arresting a suspect. 

"There was a verbal altercation that transpired. A firearm was discharged," Joe Montoya, Denver Police chief of investigations said. "An individual was shot and later pronounced deceased. There were two guns recovered at the scene." 

The shooting victim had participated in a pro-police rally, the Denver Post reported.

"The incident occurred after a man participating in what was billed a 'Patriot Rally' sprayed mace at another man. That man then shot the other individual with a handgun near the courtyard outside the Denver Art Museum," the newspaper reported. 

Denver police said they had one suspect in custody and were investigating the incident as a homicide. 

Police had a large presence at the protests to keep opposing protesters calm. 

"There was a large presence because we had two groups with opposing views, and we know that can always get very tense," Montoya said. "There’s always potential for violence, we understand that. We had a large contingent there to try to watch the egress of one group, so that the other group wouldn’t intermingle with them, so that’s the reason for the large presence there."

One side of the protests was characterized as a "Black Lives Matter Anti-Fascist Soup Drive" on Facebook. Some of the groups attending were Denver Communists, Colorado Socialist Revolution, Anon Resistance Movement, W.I.T.C.H. Denver, H.O.E.S (Help on Every Street), and Front Range Mutual Aid Network. 

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On the other side, pro-police groups organized a "Patriot Muster," local news outlet Westword reported

“We scheduled our action after learning that the militia-fascists had called a ‘patriot muster’ against the Black Lives Matter movement, anti-fascists and Marxists,” a representative for Denver Communists told Westword. “That’s us — guilty as charged and happy to oblige with our presence.”