Montreal police are describing a recent run-in with a homeless man as "unacceptable" and "unexplainable" after an officer was recorded threatening to tie the man to a pole.

Cmdr. Ian Lafreniere, head of public affairs for Montreal Police, said disciplinary action will be taken against the officer.

"This is completely unacceptable, this is unexplainable and we're sad," he said Friday.

"This is not what we expect from our police officers and there's a reason why, as soon as we got the video, we said loud and clear this is unacceptable."

Montreal's newly-elected mayor has also condemned the police officer's actions, saying the incident points to a need to better understand mental health issues.

"When we talk about mental illness, it is a complex issue," Denis Coderre said. "We're not all experts, so we have to surround ourselves making sure we're going the appropriate way."

Police said they received several phone calls about a man, dressed in a t-shirt and shorts, aggressively panhandling outside a subway station on Thursday -- a day when temperatures dropped to -40 degrees Celsius.

The officer was captured on video saying: "I've told you that if I receive another 911 call about you, I will tie you to a pole for an hour," the officer warns. "I swear -- look into my eyes -- I swear, I'll tie you to a pole for an hour."

When the man says nothing in response, camera operator Adis Simidzija steps in, telling the officer: "Those are threats you are not allowed to make, sir."

The officer responds by telling Simidzija, a Universite de Montreal student, to step back.

"The policeman was more and more aggressive, while the homeless guy was just standing there confused," Simidzija told CTV Montreal. "I was amazed by how humanless, if I can say, the scene was."

Later that night, officers and outreach workers were able to track the man down and he agreed to be taken to hospital.

Since the video was posted to YouTube on Thursday, it had been viewed more than 135,000 views by early Saturday.

Police have said the officer could face disciplinary actions that range from a verbal warning to a suspension.

With files from CTV Montreal