A video that began circulating on social media showing a man being harassed at a restaurant is under investigation by Dryden police.

Dryden Police Chief Rob Davis said officers believe they have identified both the victim and a suspect, but they have asked the public to help them find a key witness to what they are describing as a heinous crime.

"We need whoever shot the video to come forward," said Davis. "They're a critical piece of this investigation."

When Kenora resident Tania Cameron saw the video, she sent it to Dryden police, noting the victim was a First Nations man.

In the video, a younger-looking man approached the seated victim a couple of times, slapping his head repeatedly with both hands while laughing. The video, which was only seconds long, ended as the victim appeared to be getting up to leave.

Tania Cameron said she was disgusted when she saw an online video of a First Nations man being assaulted and harassed at a Dryden restaurant. She sent the video to police. (Facebook)

"I felt bad for this First Nations man who is obviously just trying to enjoy his meal at this restaurant and was being harassed and assaulted by this young punk who thought he was having a good time," said Cameron.

Davis won't speculate on whether race may have been a factor.

But Cameron, an Idle No More organizer, is concerned it might have been.

"I'd like to see justice for this First Nations man, this victim," she said. "Whether it's charges being laid against the young man or at least — at the very least — an apology."

Davis said police think the assault happened prior to March 19, when it was first reported.

He said if people see a crime, they should call police right away instead of posting a video online.