A new video of the shooting death of a knife-wielding Toronto teenager on an empty streetcar shows he was still on the vehicle when a police officer fired at him three times and was lying on the floor when another six shots were discharged.

The video, which has a clearer view of the streetcar's open doors than other footage of the Saturday incident, shows Sammy Yatim walking toward the doors when he suddenly crumples and falls to the ground as the officer fires three rounds.

Six seconds later, as Mr. Yatim remains on the floor with his legs moving, the policeman begins firing six more bullets. The security video was obtained by Global News.

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"You're able to see that the first three shots felled the young man," said Ross McLean, a former Toronto police officer and security consultant. "He certainly didn't look like he was going to spring to his feet and dash 20 yards and stick somebody."

Mr. McLean, who has analyzed several videos of the encounter, also noted that an officer issued a stern warning to Mr. Yatim just before the first shots were fired, saying: "If you take one step in this direction with that foot… [inaudible] die," according to an enhanced audio recording obtained by the National Post.

After an officer shot a total of nine bullets in 12 seconds, Mr. Yatim was also tasered. The province's Special Investigations Unit, which is investigating his death, has said Mr. Yatim "sustained multiple gunshot wounds" but has not said how many bullets struck him.

After videos taken by bystanders went viral and attracted widespread concern, Police Chief Bill Blair on Monday pledged to get to the bottom of the shooting and suspended the officer who fired the fatal shots.

The SIU, a civilian agency that investigates police incidents involving death, injury or sexual assault, has designated one "subject officer" and 22 witness officers.

Mr. Yatim, an 18-year-old Syrian immigrant who friends and family say was preparing to start college in the fall, was shot on the Dundas streetcar near Trinity Bellwoods Park early Saturday morning. Witnesses said he had brandished a knife and exposed himself before ordering passengers and the driver off the tram. A friend said he did not have a history of mental illness.