A B.C. professor who was punched by a stranger in an attack that was caught on camera is hoping someone will recognize the assailant and identify him to police.

Ray Hsu, a social justice professor at the University of British Columbia, says he was on a transit bus in Vancouver at approximately 1 p.m. on Thursday, when another male passenger aggressively shoved him from behind just as they were about to get off the bus.

Once on the sidewalk, Hsu pulled out his cellphone and took a picture of the man. That’s when the violence escalated. Hsu said he was punched and knocked to the ground.

In video shot by a someone in a car, Hsu can be seen in a headlock and being punched as he tries to maintain his balance.

Hsu said, in an interview with CTV Vancouver, that he is thankful the person who shot the video pulled over to share it with him.

But he’s disheartened that nobody offered assistance, even though he was yelling for help.

“I think the thing that worries me most, is that people can stand by and watch this happen and turn away and walk away,” Hsu said.

Hsu reported the incident to Vancouver police and gave them the video footage and the photo he snapped of his attacker.

Both are being widely shared over social media.

Hsu is hoping that someone will recognize the attacker and identify him to police.

The person who did it. 2/2 pic.twitter.com/nGQB5LaMJY — Dr. Ray (@TheWayofRay) March 3, 2017

With a report by CTV Vancouver’s Ben Miljure