The woman who captured a widely-circulated video showing an OPP officer forcefully throwing a 16-year-old Indigenous girl to the ground in Sioux Lookout on Tuesday says she was shocked as she watched the incident unfold.

Akeesha Footman captured the incident on video with her phone as it occurred as she, her sister and mother drove through Sioux Lookout, during their first visit to the northern Ontario town.

"We saw a young person sitting on a bench, with earphones in, visibly distressed, crying," she said. "There was a police officer with his hands on that young person."

Footman said her mother stopped the vehicle and rolled down the window, but the officer told them to leave.

As they drove off, Footman said she then saw the officer "being rough with the person."

They drove back, and Footman started recording the video that's been since uploaded to Facebook.

OPP assault incident 0:42

The beginning of the video shows the officer forcing the girl to the ground. There are gasps of shock from inside the vehicle, and Footman can be heard shouting "we're recording."

The vehicle drives forward, and the officer is seen appearing to handcuff the girl, who's lying face-down on the street. The officer attempts to lift her up as more police arrive, and the officer then directs one of his colleagues to go and take the information of Footman, her mother and sister.

The girl is placed in a police cruiser by several officers. Then, the officer initially involved in the altercation comes to the vehicle. During the interaction with the van's occupants, he repeatedly asks for their names, and tells them the girl kicked and spit on him.

Footman's mother tells the officer she was just trying to make sure the girl was all right.

"Why wouldn't she be all right?" the officer replies. "I'm here to help people, ma'am."

Footman's mother then tells the officer the girl looked like she was in distress.

"What kind of distress do you think she would be in?" the officer replies, and then points out a mental health worker is also on the scene assisting.

The officer also tells the vehicle's occupants it would have been "helpful" if they had assisted him while he was "being assaulted."

"You told us not to stop," Footman's mother replies. "You told me that it was none of my concern."

In the end, the no officers actually take down the names of the witnesses. However, the officer can be seen writing down the vehicle's licence plate number at the end of the video.

"I was in shock," Footman recalled. "My hand's shaking when he comes up to the car. It's hard to tell, but I'm shaking at that point because my sister's in the back seat crying. There's nothing we can do to help that young person at that point."

Footman said the chief of Lac Seul First Nation reached out and asked to see the video. Representatives of Lac Seul could not be reached for comment on Wednesday.

Footman said the girl's mother has also seen the video, and spoke to Footman.

"Nobody told her that that's the way that they treated her daughter," Footman said. "She thanked us for recording that incident."

When contacted by CBC News on Wednesday, an OPP spokesman said the organization is aware of the video, and were looking into it.

OPP did provide some more details about the arrest itself in a media release issued Wednesday afternoon.

OPP said the officer had been notified about the girl by a member of the public, who was concerned for her safety.

The girl, OPP said, was known to police, and was "highly intoxicated" when located on Fifth Avenue. As the officer attempted to arrest her, he was assaulted.

The girl is facing assault charges, and appeared in Dryden court on Wednesday.

Sioux Lookout Mayor Doug Lawrance said Wednesday he'd seen the video, and spoken to the chair of the town's police services board, as well as the local OPP inspector about it.

"The video is really like a snapshot," he said. "We don't have the information that led into that. We don't have the follow-up. I know that the police inspector said he'd be following up with the officers."

"I think that, in general, the police do an excellent job of dealing in Sioux Lookout with social situation that are left in the laps of police due to gaps in services," he said. "We have no detox, we have no addictions treatment centres, we need a fully-resourced emergency shelter."