TORONTO -- WARNING: The story contains graphic video

CTV News has obtained footage that appears to show a RCMP officer punching and tackling an Alberta First Nations chief during an arrest in March.

Athabasca Chipewyan First Nation Chief Allan Adam said that he was leaving a casino in Fort McMurray, Alta. after 2 a.m. on March 10 when officers confronted him, his wife and his niece about an expired licence plate tag.

The nearly 12-minutes of footage shows an RCMP vehicle pulling up behind a parked pickup truck while Adam calmly walks towards the driver's side of the police cruiser. After a short time, Adam is then seen walking back to the truck, appearing to grab something before returning to the cruiser.

"I'm tired of being harassed by the RCMP," Adam is heard saying in the video. "F—king leave us alone. Don't f—king stop behind us like you're f—king watching us."

Adam is then seen walking back to the truck for a short time before returning once again to the RCMP vehicle. An officer is heard telling Adam to return to his truck.

"You and I are going to have a f--king problem, right here, right f--king now," Adam said as he stood in front of the police cruiser.

About three minutes into the video, an officer is seen leaving the cruiser and approaching the First Nations chief, who is standing behind his truck. The officer then begins speaking with Adam's wife, who is in the driver's seat of the truck, while Adam enters via the rear passenger-side door.

A few minutes later, an apparently agitated Adam is seen jumping out of the truck and removing his jacket as he approaches the officer. Adam's wife is seen leaving the truck too, appearing to try calm her husband down. Adam tosses his jacket into the truck before appearing to get into a fighting stance. Adam then walks around the truck and gets into the rear passenger side seat again as the officer and his wife follows behind.

The officer then turns to Adam's wife, grabs her arm, twisting it. That's when Adam jumps out of the truck yelling at the officer to "leave my wife alone" before knocking the officer's arm and getting into the fighting stance again. The officer is seen placing his right hand on his hip, appearing to place his hand on his weapon.

It's not until approximately seven minutes into the video when Adam is seen behind the truck once again as the officer grabs Adam's arm in what appears to be an attempt to place the First Nations chief into custody. Almost immediately, a second officer is seen charging at Adam and appears to tackle him to the ground by his neck. The second officer is then seen apparently punching Adam in the head.

"What the f—k is wrong with you?" Adam is heard saying while pinned on the ground. Officers placed handcuffs on Adam before picking him up off the ground. Adam's face is seen bloodied before he’s placed into the RCMP vehicle.

On Saturday, Adam held a press conference in Fort McMurray where he alleged he was beaten during the arrest. Adam told reporters he asked the officer why he was being harassed and identified that he was the chief of the Athabasca Chipewyan First Nation.

“Whatever their intentions were of doing startled me because, why are they coming after me and why are they going after my truck?” Adam said. “I told my wife, ‘We can’t go nowhere,’ and my wife said, ‘What?’ And she put the vehicle in drive and was just going to drive away and the RCMP officer came knocking on the window and screaming and everything from outside and he said stop, so she stopped."

That’s when they were told not to move the vehicle because of a registration issue and an argument ensued.

"I looked up, and out of nowhere the second officer who was the first officer on scene after he was called in, he just gave me a what you would call in the wrestling world a clothesline,” Adam said Saturday. “It was just like a tag-team match where one officer holds me by the arm and the officer just comes and bridges me across the cheek and when I saw them coming I moved to the left, cause if I didn’t he would have bridged me on my nose and busted my nose.”

“I dropped to my knees and slowly I could feel that I was going unconscious and all I could remember just the blood that was gushing out of my mouth and there was a deep laceration inside of my mouth and blood was just pouring out of it.”

Chief Adam was later charged with resisting arrest and assaulting a police officer in execution of duty.

The video of the incident was reviewed by superiors as per policy, RCMP said originally, and it was determined that the officers' actions were reasonable and didn’t meet the threshold for an investigation. On Saturday afternoon, however, RCMP announced the Alberta Serious Incident Response Team would look into Adam's accusation that the officers assaulted him.

“The RCMP and the Director of Law Enforcement with the Ministry of Justice and Solicotor General's office in Alberta have discussed this incident," a statement read.

"An independent investigation into incidents involving police are important as it contributes to the trust and confidence the public has in their police service."

Adam is scheduled to appear in Wood Buffalo Provincial Court on July 2, 2020.

--with files from CTV Edmonton's Laine Mitchell