Pinkerton security guard is charged with murder after shooting dead Navy veteran, 49, at 'Patriot Muster' protest in Denver

Matthew Dolloff, a television station security guard is accused of fatally shooting a pro-police demonstrator following opposing rallies, has been charged with second-degree murder

A television station security guard accused of fatally shooting a pro-police demonstrator following opposing rallies was charged Monday with second-degree murder, according to the Denver district court clerk´s office.

The charges in the death of Lee Keltner, 49, were filed to the district court against Matthew Dolloff, 30, who was protecting a KUSA-TV producer at the time of the incident.

The next hearing is set for Wednesday morning, according to the district court clerk´s office. No attorney has been listed for Dolloff yet in court records.

People convicted of second-degree murder face a mandatory sentence of between 16 and 48 years in prison.

William Boyle, a lawyer for Keltner´s widow, said Friday that he thinks the evidence available supports a second-degree murder charge.

Keltner was a US Navy veteran. At the time of his death, he was taking part in a pro-police 'Patriot Muster' rally 

Under Colorado law, second-degree murder is defined as knowingly killing someone but without the deliberation prosecutors are required to prove in first-degree murder cases.

Boyle said he has reached out to KUSA-TV, Pinkerton and Isborn Security, the security company that said it hired Dolloff for the work as a contractor to Pinkerton, seeking more information about their actions. He said he did not immediately hear back from them and that a lawsuit against any entity involved in allowing Dolloff to work without a license was a possibility in order to 'open a conversation.'

'We are just trying to find out exactly what happened, why it happened and who is responsible for creating the situation that resulted in Mr. Keltner´s death,' he said.

Police say Keltner was in a verbal dispute with a 27-year-old man as the rallies broke up Saturday when Dolloff and a 25-year-old person got into an altercation with Keltner.

This image captures the moment Keltner sprays mace, left, as Dolloff, right, fatally fires a semiautomatic gun at him in Denver

Keltner staggers backward after Dolloff fired his weapon into the cloud of mace

In this October 10 photo, Dolloff, a TV station security guard, right, turns after fatally shooting Keltner following opposing rallies

Dolloff drops his gun and kneels with his hands in the air as he is taken into custody after the fatal shooting. He could face up to 48 years if convicted of second-degree murder

Keltner slapped Dolloff in the head and Dolloff pulled out a semiautomatic handgun and shot Keltner as Keltner discharged pepper spray at him, police said in an arrest affidavit.

A cellphone video taken by KUSA´s producer suggests that Keltner was upset that his dispute with the first man was being recorded by cameras.

It shows Keltner in a confrontation with a man wearing a T-shirt that read, 'Black Guns Matter.' A bystander is trying to defuse the argument, which occurred after a 'Patriot Muster' demonstration and 'BLM-Antifa Soup Drive' counterprotest downtown.

The video then shows Keltner, holding a spray can, walking out of view. A man´s voice - it´s unclear if it´s Keltner - is heard saying the area was no place for cameras.

'Get the cameras out of here or I'm going to f*** you up,' the unidentified man says. Keltner and Dolloff are then shown scuffling before the video stops.

The producer resumes filming after the shooting and tells arriving police that he is with the press and says of the man who was shot, 'That guy was going to get me.' He also says the security guard shot Keltner because Keltner used mace.

Someone out of view can also be heard saying 'he´s got magazines in his coat' but it is not clear who the person is talking about.

Police said they found two guns but they have not explained who they belonged to.

WHO ARE THE 'PATRIOT MUSTER' PROTESTERS?

Patriot Muster is the name given to pro-police activists who have attended rallies organized by John Tiegen, an ex-Marine and Blackwater private security guard. 

The group was formed over the summer as Denver, along with dozens of other cities across the US, was roiled by protests against racism and police brutality. 

Patriot Muster made headlines in July when it hosted a 'Back the Blue' rally that descended into chaos when protesters began clashing with counter-protesters. Tiegen accused the counter-protesters of throwing soup cans at his followers. 

Tiegen organized another Patriot Muster rally on Saturday at the Denver Civic Center, under the slogan: 'Stand up, show up.'

The slogan bore similarities to President Donald Trump's response when asked to condemn white supremacists and the Proud Boys. Instead of disavowing them he said: 'Stand back and stand by.' 

Black Lives Matter protesters led by the Denver Communists responded by creating their own rally in the same location, dubbed the 'BLM-Antifa Soup Drive'. 

The 'soup rally' was meant to be ironic in response to Tiegen accusing leftist protesters of throwing cans. 

Tiegen foreshadowed violence at the event on Friday, telling KNUS: 'I'm not going in there to do violence, but I'm going to be prepared to do violence.'