Sgt. Randy Fincham said a Twitter user directed the police force to the online video, which shows a man kicking two other men along what appears to be the Granville Street entertainment district in the city's downtown. The specific date and time aren't clear.
In the video, the first apparent volunteer flinches and it's not clear how hard or where he is hit. The second man is kicked in the groin but quickly runs away, prompting the kicker to chase him, after which it appears the second volunteer is attacked across the street.
Fincham said the man who police believe is responsible for the kickings has already contacted them and he's co-operating. Investigators also believe they know the identities of the men who were kicked.
"Taking advantage of another person with the promise of money to compensate them for injury is distasteful and extremely concerning to the police department," Fincham told reporters.
"Although a person does have the right to consent to being hit, the actions leading up to and following the kick are being investigated as a criminal offence."
Fincham said investigators want more information about what happened, such as the conversations that led up to the first person being kicked.
They also want to gather more information on what happened after, he said.
Fincham had little information about the background of them who were kicked in the video.
"The concern for us at this point is the actions of the person that appears to have kicked these people," he said.
"Why somebody in society would feel that would be necessary or appropriate to engage in an act like this, or why somebody else feels that in order to make money they need to subject themselves to some form of physical violence ... that' the crux of what we're investigating at this point."
Riley Speers, a 19-year-old Vancouver resident, identified himself to The Canadian Press as the person who shot the video and posted it online. He said he witnessed the incident at about 3 a.m. early Monday while leaving a local night club.
He said people were panhandling outside the club, and they were approached by a man who was walking down the street.
"And he (the kicker) is like, 'Here's $50 if you let me kick you in the balls,' and he put the money on the pavement," said Speers.
Speers said it didn't appear as if anybody was hurt, and he posted the video online because he wanted to raise awareness about the situation.
"There's people in our city that are willing to take money to get like assaulted," he said.
Meanwhile, Fincham said it's alarming that people stood by and watched the incident but didn't call police.
Investigators want to speak to witnesses and are looking for more video of the incident, said Fincham. He said police will also review video that was shot in the area at the time.
Fincham said it was the first time he'd heard of such an incident taking place in Vancouver, although he did some research Thursday and learned similar incidents had taken place around North America.