Security videos obtained exclusively by CBC News show what experts are calling an "assault" of an alleged truck thief by Edmonton police during a violent arrest was far worse than previously revealed.

The Alberta Serious Incident Response Team (ASIRT) is investigating the June 11 arrest of Kyle Parkhurst after witness cellphone videos posted on social media showed an officer repeatedly kicking a prone Parkhurst, slamming him head first into a brick wall, then shoving him against a cruiser while he was handcuffed.

But security video — never before made public — shows an officer struck Parkhurst in the head with either a handgun or a Taser, and another officer delivered an elbow smash to the handcuffed prisoner's head.

"I'm deeply troubled by it," said Amanda Hart-Dowhun of the Criminal Trial Lawyers' Association. "Some of the use of force within those videos is, in my view, very excessive to anything that would be required in the circumstances.

Security video obtained by CBC News along with civilian cell phone video reveals the full extent of police violence in the June arrest of an alleged truck thief. The videos show the alleged thief being struck with what appears to be a gun before he is repeatedly kicked, thrown headfirst into a brick wall, elbow smashed in the head and then pushed hard against a cruiser. Officers then appear to re-enact the violence. 1:36

"It is clear to me that at least part of this force is a product of anger and a desire for him to pay for what he [allegedly] did, rather than as an attempt to prevent him from committing a further offence or injuring someone," Hart-Dowhun said.

Citing the ongoing ASIRT investigation, Edmonton police Chief Dale McFee has declined interview requests from CBC News.

Security videos show arrest

ASIRT took over the investigation in July after CBC News revealed Parkhurst alleged he had not received proper medical care for two weeks after the arrest. Parkhurst, 26, does not remember the arrest, which Hart-Dowhun said is not surprising given the number of head blows he sustained.

In addition to a civilian video, CBC News has obtained video from two security cameras that show opposing angles of the arrest and provide a fuller picture of what transpired.

Parkhurst, driving an allegedly stolen truck, backs into a parking stall in what appears to be an attempt to hide from police. When one cruiser blocks him in, he reverses over a concrete barrier then backs into a power pole. Blocked again, he looks for an escape route near the side of the building. Cruisers box him in from behind and in front and he rams them before he is forced to a stop.

Amanda Hart-Dowhun with the Criminal Trial Lawyers' Association says that after viewing the videos, she was 'deeply troubled' by the force police officers used during the arrest. (Scott Neufeld/CBC)

An officer jumps from the passenger side of one cruiser, aims what appears to be his gun at Parkhurst's vehicle, then approaches. Parkhurst opens the truck door and begins to get out. At this point, officers are yelling at him to get out of the truck and get on the ground.

The officer kicks the truck door against Parkhurst and then — in a move previously not visible in the witnesses' cellphone videos — strikes Parkhurst in the head with his weapon.

"We don't pistol whip people in Canada. That in itself is just unacceptable," said Kelly Sundberg, a Mount Royal University criminologist and use-of-force expert.

Sundberg said that had the weapon been a gun, the officer would have risked an "unintentional discharge" that could have endangered Parkhurst, another officer or a member of the public.

Prisoner elbow-smashed in head

After being struck in the head by the weapon, Parkhurst falls to the ground and is immediately swarmed by several officers. The security cameras show officers stomping and punching him as he's on the ground. Police confirmed he was also Tasered twice.

At one point, a bald officer looks over both shoulders, then kicks Parkhurst three times as he's on the ground. The same officer hauls the handcuffed prisoner to his feet and slams his head into the building's brick wall.

The building's cameras, unlike the cellphone videos, capture what happens next. After another officer pushes Parkhurst against the side of the truck, the bald officer smashes his elbow into Parkhurst's head.

'What really struck me is the number of times that this individual was hit aggressively by members of the police,' says Mount Royal University criminologist Kelly Sundberg, a use-of-force expert, about the video footage. (CBC)

The bald officer then walks Parkhurst toward a cruiser and violently slams him into the side of the vehicle.

"What really struck me is the number of times that this individual was hit aggressively by members of the police," Sundberg said.

"Of great concern is when he is in handcuffs and clearly he was not resisting or offering a level of resistance that would justify any hitting or kicking."

Video contains evidence of assaults: lawyer

Hart-Dowhun, a criminal defence lawyer, said the videos show clear evidence of several assaults.

She said the officer who struck Parkhurst with his weapon could be charged with assault with a weapon. Hart-Dowhun also said the officer who kicked Parkhurst, threw him head first into a wall and elbow-smashed him could be charged with assault or assault causing bodily harm.

Both Sundberg and Hart-Dowhun independently noticed an officer, who appeared to be a sergeant, turn and walk away from the scene of the arrest as officers began to strike Parkhurst.

"It would appear that there was a supervisor on scene, and there are a lot of officers on scene, and no one stopped — or even appears to attempt to stop — the assault on this individual," Sundberg said. "And that is really concerning."

After the cellphone witness videos of the arrest were posted online in June, sparking media coverage, EPS announced its professional standards branch was investigating.

The police chief later confirmed one officer had been removed from active duty. That officer's identity has not been disclosed.

But the police service did not disclose it was also conducting a criminal investigation into the arrest. CBC News only learned about that investigation from Alberta Justice after seeking to determine why EPS had been allowed to investigate a potential assault on a prisoner.

A day after the CBC News report, Edmonton police announced ASIRT was taking over that investigation.

Police shouldn't mete out 'street justice,' expert says

Parkhurst faces a total of 84 recent charges, and has seven convictions dating back to 2014.

In court in July, a Crown prosecutor detailed dozens of charges against Parkhurst for stealing vehicles, credit cards and other valuables. The charges portrayed Parkhurst as an out-of-control, methamphetamine-addicted car thief who repeatedly endangered the public while fleeing police.

Parkhurst is being held at the Edmonton Remand Centre after a provincial court judge denied bail, ruling his lengthy history showed he poses an "extreme" risk to the public.

Sundberg said Parkhurst's criminal record and alleged crimes do not justify the beating, which he said undermines the police service's credibility.

"The police are not involved in carrying out the punishment for crimes, let alone making the judgment of a crime," he said. "That's what the courts are for.

"The police function is to investigate, and apprehend, and ensure our safety, not to implement some sort of street justice."

If you have information for this story, or information for another story, please contact us in confidence at cbcinvestigates@cbc.ca.

@charlesrusnell @jennierussell_