An Ottawa police officer who shot and killed a stabbing suspect outside a grocery store last year will not face charges, Ontario's police watchdog said Wednesday.

The incident began when a 25-year-old man stabbed a 49-year-old man inside the Metro store on Wellington Street W. near Island Park Drive on Feb. 25, 2018.

The suspect was later shot and killed by an Ottawa police officer.

The Special Investigations Unit's report, dated Jan. 21, offered more details about the incident.

Man gave 'battle cry'

According to the SIU report, security footage showed the suspect chase the other man inside the store before stabbing him and fleeing.

Witnesses told responding police officers the man had fled to a nearby house that was under construction.

A male officer approached a dark, narrow passageway between the house and another home from the rear with his gun drawn because he was expecting to encounter an armed suspect, the SIU said.

The confrontation occurred in a narrow passageway between two homes, the dark space at the centre of this photo. (SIU)

That officer told the SIU he heard a "battle cry" before the suspect jumped out about a metre-and-a-half in front of him, a knife raised at shoulder height.

The officer told the suspect to drop the knife, but the man took two steps toward him and the officer fired three shots.

The officer said the suspect hunched over but came at him again, so he fired three more shots.

A 25-year-old man was shot and killed by an Ottawa police officer near the Island Park Metro on Feb. 25, 2018, leading to an investigation by Ontario's police watchdog. 0:23

No time for Taser

This time the suspect stayed down, and was later pronounced dead in hospital.

The SIU said an autopsy showed the officer shot the suspect five to six times, including three times in the chest.

The officer told investigators he didn't have time to deploy his Taser.

"[He] told the SIU that he was aware the [suspect] had already stabbed someone and that he feared for his safety," wrote SIU director Tony Loparco.

"He felt that [he] was going to stab him and that he was unable to escape because he was in a confined space and the ground was slippery from the ice."

The narrow passageway where the suspect was shot and killed. (SIU)

Loparco said one witness saw part of the shooting, and several others heard it.

"The [suspect] let out a cry indicative of an intention for further violence, ignored commands to drop the knife and advanced towards the officer with the knife raised," he said.

"An objective bystander clearly would consider the officer's belief that he was going to be stabbed [to be] reasonable."

The SIU assigned 11 investigators to the case and talked to 10 civilian witnesses and eight officers, including the one who fired the shots.

The SIU is an arm's-length agency that investigates incidents involving police in which someone is killed, injured or alleges sexual assault.