THE right-wing protester allegedly killed by a security guard during clashes with Antifa was shot dead in the head in front of his son.
Military veteran and grandad Lee Keltner was shot after macing the guard for the 9NEWS TV crew on Saturday during dueling rallies in Denver.
The 49-year-old veteran is believed to have been taking part in a "Patriot Muster" rally, and was fatally shot at around 3.30pm outside the Art Museum in .
The suspect has been identified as 30-year-old Matthew Dolloff, with the Denver Police Department saying he's being investigated for first degree murder.
A Facebook page with Dolloff's full name and a photo that appears to match his mugshot shows that he worked on a ranch raising sheeps and dogs, the reported.
Court records obtained by the newspaper show he had no previous criminal history aside from traffic tickets.
Denver police arrested Dolloff on suspicion of shooting and killing a man after a clash at the protests downtown.
Photos of the incident taken by the show a man slapping Dolloff and use pepper spray near the Denver Art Museum.
Moments later, Dolloff then shot the man, according to the photos.
Carol Keltner, who identified herself as the victim's mother, shared the update in a Facebook group called Northeast Arkansas Tea Party Group.
"My son Lee was at the patriot rally today in Denver," .
"After the rally a person on the and side went up to him said a few nasty words then shot him in the head. He was murdered because he backed the police," she continued.
"His 24 year old son was with him," she added. "I moved to because got too expensive and liberal. The left has gotten out of hand."
Jay Keltner, who identified himself as the victim's son, also posted to Facebook about his father.
"I can't believe my dad's gone," he wrote. "This will never be right #RIP."
Jay Keltner told The Sun that he was not with his dad at the rally.
Suzan Keltner, the sister of the victim, that the son who was present at the rally is having a difficult time coping after his father was killed.
"He was there," she said. When asked if her nephew was doing OK, she said, "No, no he's not."
She later added: "There's going to be a lawsuit, so I'm not sure how much we can let out."
Keltner was described in other social media tributes as a “loving husband, father and friend” who would help those in need.
Friend Laura Sanders wrote on Twitter: “Lee was a loving husband, father & friend. He was a minister & helped those in need. He has family & friends who are grieving.”
She wrote in another message: “Lee u always had a great sense of humor & always helped those you could. U were one of the good guys! This world is a sadder place without u my friend! Thanks 4 all the great memories & fun times! Praying 4 your family! U were an amazing friend, husband and dad! Love ya buddy!”
Laura added: “I will miss you forever my dear friend! Your life taken by a coward! You were an amazing husband, father and friend! I will miss our conversations and your laugh and smiling face! Rest In Peace Lee! Much love.”
The 49-year-old father of two ran a business, Crossfire Hats in Brighton, as a specialized hat maker.
He told the in 2015: “Everything I do is custom. I do one hat at a time, I do it right for that customer, and then I move on to the next one.”
Keltner, talking about his business in a 2012 video said he was "keeping the West alive, one hat at a time."
He said: "The cowboy hat is the history of the West" and added in Colorado the cattleman style was the most popular.
"I love being an artist," Keltner said. "Creating new and different things because I do all the work myself and I do it one at a time. It's truly special for that customer."
On Saturday, after Keltner is said to have used the mace, the suspect reportedly pulled out a handgun and shot him at point blank range.
He was taken to the hospital, where he died an hour later, Denver Police Investigations Division Chief Joe Montoya said.
It was later reported by that Dolloff was a contractor the news station hired through Pinkerton.
"A 9NEWS employee and a 9NEWS contractor were taken into custody," the station said, noting that the second of the two people wasn't connected to the shooting.
The producer was later released from police custody, but Dolloff was detained by DPD later into the evening.
For several months, 9NEWS has hired private security guards to accompany staff at protests, the news station said.
Video shared on by prominent pro- conservative Ian Miles Cheong claims to show the verbal altercation that led up to the shooting.
A man wearing a "Black Guns Matter" shirt urges a tattooed man wearing a camouflage bucket hat to mace him.
"Mace me, f**kin' mace me brother!" the man yells. "Walk up to me and f***ing mace me n****, mace me mother f****r!"
A woman can be heard in the background asking the man why he's using a racial slur as he continues to shout at the counter-protester.
The bucket hat man clutches what appears to be a can of mace as the two continue to exchange obscenities.
"F**k around and find out!" the man with the Black Guns Matter shirt screams before turning his attention to another man holding a baton.
Moments later, the victim is seen dropping to the floor behind the arguing men after the hiss of an aerosol can and a loud bang.
Two guns were recovered at the scene, and the suspect in custody is being held at police headquarters, DPD said.
A canister of Mace was also recovered at the scene, and detectives are still probing whether it was used in the attack, the police chief said.
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The security guard still had his handgun in his clutches, and as cops swarmed him with their guns pointed, he dropped to his knees, raised his hands above his head and released his weapon.
He was arrested at the scene along with the second person, who was later believed to have no connection to the shooting.
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Local businesses were warned of the potential for escalating violence early Saturday and were told to report seeing protesters wearing helmets, shields, or gas masks ahead of the rallies, KMGH reported.