The Toronto police officer charged with fatally shooting a teenager on a streetcar in 2013 testified in court Thursday that knowing what he knows now, he wouldn't have unloaded a second round of gunshots at the 18-year-old, but would have still fired the first round.

In Ontario Superior Court, Const. James Forcillo called Sammy Yatim "one of the most determined people I've ever had to deal with." Despite clear orders, he said the 18-year-old was defiant and unafraid during the final moments of his life.

"I am pointing a firearm at him at 10 feet or less and he couldn't have cared less," the 32-year-old officer told court Thursday.

Check out the recap for our live blog for the trial of Const. James Forcill, which began Wednesday and continued Thursday. The live blog is posted at the bottom of this story.

Forcillo has pleaded not guilty to charges of second-degree murder and attempted murder in the July 25, 2013, fatal shooting of Yatim, who was alone on an empty streetcar with a knife in his hand when he was shot eight times.

The driver of the 505 Dundas streetcar had fled the vehicle as had other passengers after Yatim exposed himself and waved the knife around.

Forcillo told court he believed Yatim chose not to comply with orders despite loud, clear instructions, adding the teen appeared unafraid and his face was clenched and his body appeared tense. He described the situation as the calm before the storm, maintaining he thought Yatim was coming off the streetcar and posed a threat.

If I had known everything I do now, I would never have taken the second volley. - Const . James Forcillo , Toronto police

"He was showing me the knife," Forcillo said of his first glimpse of Yatim, adding he didn't pull out his gun until he saw the knife, which is what he said his training has taught him. The officer said in Yatim, he saw a young, fit man who could move quickly with a knife in his hand.

"As a police officer, we're always at a disadvantage when it comes to reaction times. Having your firearm out takes a few seconds off that equation," the officer said. "If I'm injured by the person with the knife, I'm unable to protect other people on the street."

Forcillo said he was forced to make the biggest decision of his life prior to shooting Yatim.

For a second, the officer said it appeared that Yatim was listening to his commands. At first, the teen did move back slightly when told to, but then moved forward again, the officer said. When he ordered Yatim to drop the knife he was holding one last time, he said no, according to Forcillo.

The officer said if Yatim had decided not to advance at that point, "he wouldn't have gotten shot, none of us would be here."

After firing three shots, Forcillo said he knew he had hit Yatim but did not know where because he couldn't see any blood. He said he then paused to assess the situation and saw Yatim had dropped the knife, which was a few inches away from his right hand.

Officer recounts final moments

The officer admitted that security videos from that day show Yatim did not try to get up after being shot. He said no one was more shocked than he was to see on video that Yatim didn't attempt to get up.

Forcillo said he believed Yatim chose not to comply with orders despite loud, clear instructions, adding the teen appeared unafraid and his face was clenched. (TTC security video) "If I had known everything I do now, I would never have taken the second volley," he said. But the officer maintained he would not have done anything differently when firing the first shots at the teen. He fired a further six shots after Yatim was on the ground. An autopsy determined the teen was struck by eight bullets.

Overall, Forcillo said Yatim looked like "that guy in the bar looking for a fist fight."

For a second, Forcillo said it appeared that Yatim was listening to his commands. At first, the teen did move back slightly when told to, but then moved forward again, the officer said. When he ordered Yatim to drop the knife he was holding one last time, he said no, according to Forcillo.

The officer said if Yatim had decided not to advance at that point, "he wouldn't have gotten shot, none of us would be here."

'His behaviour was unreasonable'

The officer testified he drew his gun shortly after spotting the knife in Yatim's hand, an act he said is consistent with police training on how to handle a confrontation with someone holding an edged weapon.

Forcillo said he drew his gun to show Yatim the seriousness of the situation and to let the teen know that he would be in danger if he didn't comply with his commands.

Having the gun ready would have saved time in the event Yatim charged, Forcillo testified.

Forcillo also testified that from his position on the street outside the streetcar door, he could not see that the streetcar was empty. Forcillo said Yatim did not heed his order to drop the knife.

"My order was reasonable," said Forcillo. "His behaviour was unreasonable."

To follow Thursday's testimony, watch our live blog below.