07/29/2013 08:40 EDT | Updated 09/28/2013 05:12 EDT

Streetcar shooting video raises questions over police lethal force

The amateur video that shows Toronto police fatally shooting an 18-year-old man armed with a knife on a downtown streetcar on Saturday raises serious questions about how police handled the confrontation, a security expert and former Toronto police officer says.

Ross McLean studied a version of the video with enhanced video and audio, frame by frame.

Witnesses say Sammy Yatim was alone on the 505 Dundas streetcar near Trinity Bellwoods Park when he was shot just after midnight Saturday morning. He had pulled a knife and ordered everybody off the streetcar, witnesses say.

The original video posted online shows the stopped streetcar at a distance, with multiple police officers nearby, at least one with his hands raised to shoulder height.

Nine gunshots are heard within 13 seconds.

On the enhanced video, a six-second jolt from a Taser can be heard after the gunshots, McLean said. Yatim also appears to put his hands over his head at one point on the enhanced video, he said.

'Your mouth is your best weapon'

McLean says if the officers had waited another minute for the officer with the Taser to arrive instead of opening fire, Yatim might be alive today. "Should you be Tasering someone who’s been shot six or nine times and lying on the ground?” he told CBC News.

McLean says the video also suggests police did not engage the suspect.

"Your mouth is your best weapon," he said.

The key is to communicate with and contain the suspect, he said.

"He was fairly contained. He was in the streetcar. He could have let that guy sit there all night."

Police can be heard on the enhanced video saying "Drop the knife!" and "If you take one step in this direction, you’re finished," McLean told CBC host Matt Galloway on Toronto's morning radio program Metro Morning.

McLean said it's unlikely that any of the nine shots were warning shots.

"This officer’s going to have to explain why he used the level of force he did," McLean said.

Ontario’s police watchdog is looking into the shooting. The Special Investigations Unit investigates all incidents involving police in which someone is injured or killed.

McLean said police Chief Bill Blair should speak about the shooting.

Blair's office originally told CBC News they wouldn't speak about the case because they are legally bound not to discuss an incident under an SIU investigation, but police then said Monday morning that the chief will make a statement at 11 a.m. ET.

Vigil today

Yatim’s family and friends are holding a vigil at the site of the shooting Monday evening.

The family, which moved to Toronto from Syria about five years ago, is hiring a lawyer and wonders how police could shoot him multiple times even after it appears he went down.

His sister, Sarah, said her family is in shock.

Yatim's friends have posted their condolences for the recent high school graduate on social media, and Sarah has started a Facebook group that she hopes will help stop what she considers an injustice at the hands of police.