Open this photo in gallery A screen grab from a Twitter video shows the suspect being arrested in Toronto on Monday. Clark Hua Zhang/Twitter

After plowing down dozens of pedestrians in what Toronto police are calling an “unprecedented” event, the suspect in Monday’s fatal van attack emerged from his vehicle and faced off with a police officer.

Video from the scene shows a black-clad man quickly and repeatedly drawing and aiming an object at a police officer, shouting at the officer to kill him. The officer ignores the demand and continues to advance slowly with his firearm drawn.

Not a single shot was fired during the dramatic exchange and the officer is being lauded for his cool-headed arrest.

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In the video, the officer shouts: “Get down!”

“Kill me!” the man replies.

“No, get down!”

The suspect tells the officer he has a gun in his pocket, to which the officer replies that he doesn’t care. The officer orders him again to get down, warning he will be shot if he doesn’t. The man tells the officer to shoot him in the head.

The officer hastens his pace and approaches the suspect, who then drops what he was holding and raises both hands. The officer gets the suspect on to his stomach and puts handcuffs on him.

Bystanders captured the moment one police officer arrested a suspect after a white van ran over dozens of pedestrians on Yonge Street between Finch Avenue East and Sheppard Avenue East in Toronto. The Globe and Mail

Toronto Police Chief Mark Saunders was asked at a news conference about how Monday’s arrest compared with previous incidents with officers in which there appeared to be less of a threat and which ended in gunfire − such as the killing of 18-year-old Sammy Yatim in 2013 − but he would not discuss such comparisons.

Speaking generally about Monday’s arrest, he earlier praised the training of his officers. “The officer [on Monday] did a fantastic job with respect to utilizing his ability of understanding the circumstance and environment and having a peaceful resolution at the end of the day.”

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Mike McCormack, president of the Toronto Police Association, said the officer did exactly as he was trained to do.

“The officer would have been doing a continual threat assessment,” he said.

An officer would have been justified in discharging a firearm in such a situation, Mr. McCormack said, “but this officer looked at what was going on and determined he could handle it the way that he did. People are right: This guy is a hero.”

Mr. McCormack said he has spoken with the officer, whom he believes is in his 30s and has been with the force for more than seven years. The union president said the officer, a humble and easygoing guy, is “shaken” – not by the arrest, but by the carnage preceding it.

“He said, ‘Mike, I just did my job. What I did was no big deal. But look at these poor people,’ ” Mr. McCormack said. “That’s what everyone’s thinking: Great, he did his job and arrested this guy and may have prevented further deaths. But he’s more concerned with 10 people being dead, 15 people being injured, why now and what’s happening in this city.”

Former Toronto homicide detective Michael Davis, who heads security agency Michael A. Davis Investigations, praised the officer’s response and said he had to have felt he was in control and confident that he could handle any of the suspect’s moves.

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“He showed tremendous restraint. I’m sure it took tremendous strength,” Mr. Davis said, adding that he was grateful that the suspect is alive, as he could help investigators determine a motive.

Chief Saunders confirmed on Monday night that the suspect is Alek Minassian, 25, from Richmond Hill. Public Safety Minister Ralph Goodale said that while Monday’s events were “horrendous,” there appears no be no threat to national security.

A Toronto resident who was driving near a van when it mounted a sidewalk and hit pedestrians says he repeatedly honked his horn to alert bystanders to the horrific incident. The Canadian Press

Subhendu Basu, 49, an accountant, was driving in the area when he witnessed the arrest. He said he was stunned to see what was unfolding before him and described the scene as being “just like a movie.”

“The police officer overpowered him and pushed him down to the road and then other officers came running,” Mr. Basu said. “That guy was great, man. It happened so fast. Right now I’m in a kind of trance.”

The Toronto Police Service’s Employee and Family Assistance Program will provide emotional and situational support to affected officers, Mr. McCormack said. As well, officers will undergo critical incident stress debriefing.

“This is a hugely traumatizing incident for all our members,” he said. “This is unprecedented. Even in my over 30 years, to be on a scene like that − you see it on TV and you think it’s in another place, it’s in Europe, but now it’s here. To see the actual carnage and the bodies lying on the streets of Toronto, I think it’s changed the city forever.”

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With reports from Joe Friesen, Tu Thanh Ha and Oliver Moore