Ottawa Police Chief Charles Bordeleau has authorized an investigation after an officer was captured in a video punching a man in the face outside the Salvation Army shelter on George Street on Monday afternoon.

Mirna Guerrero recorded this video of an Ottawa police officer punching a man outside the Salvation Army shelter. 0:23

Mirna Guerrero said she later witnessed the same officer push a woman to the ground outside the shelter on George Street after the woman asked for his badge number.

As hard as it is for the public to see, they have to understand the entire context of it. - Matt Skof, Ottawa Police Association

"I have a lot of respect for police officers — I thank them for what they do — but that was unacceptable," she said. "A police officer shouldn't be using excessive force."

Matt Skof, head of the Ottawa Police Association, said the man was drunk and combative before he was punched by the officer.

"As hard as it is for the public to see, they have to understand the entire context of it," he said.

A man who refused to be named told CBC News that the white man captured in Guerrero's video was drunk and shouting racist obscenities at the arresting officer, who is black.

"He started calling the officer the N-word, over and over and over. And the officer gave him a blow to the head," he said.

But Guerrero said the punch appeared to be unprovoked.

'Powerful punch'

Mirna Guerrero recorded an Ottawa police officer punching a man outside a shelter. (CBC) Guerrero was in a car on George Street around 4:30 p.m. Monday when she said the officer, who she described as a "big guy," got out of his cruiser.

"Someone was being noisy or something. The person was standing on top of a set of stairs and out of nowhere (the officer) just grabbed him by the shoulders and he threw him down on the floor," Guerrero said.

"I took out my camera because I thought there was going to be more violence."

Guerrero said the man "wasn't doing anything" when the officer hit the man with a "powerful punch," causing him to bleed from a gash on his forehead.

Tyler Kahnt said witnessed the punch, too.

"His nose was wide open and then he probably needed stitches in the cheek, too, from the hit," he said. "You've got cuffs. Put the guy in cuffs and do it the proper way."

2 officers allegedly pushed woman

A paramedic parked nearby approached the officer and told him to "calm down," Guerrero said.

"You could tell the police officer was aggravated," she said.

They were just scary. It was very upsetting. - Mirna Guerrero

Guerrero said she saw the officer push a woman who was "a lot smaller than him" to the ground.

A second officer then pushed the same woman to the ground a second time, Guerrero said.

"They were just scary. It was very upsetting," she said.

The officers involved "don't deserve to wear the badge," said Guerrero, adding that she hopes they are disciplined for their actions.