Testifying in his own defence, Christopher Husbands also said he does not remember exactly what happened in those terrifying seconds when he said he looked up and saw two men he believed were about to shoot him.
"I was afraid, I was panicking. I wasn't expecting to see these people. They just came out of nowhere," Husbands said.
"I was shocked. I was caught off guard."
Video surveillance footage shows Husbands opening fire, including pumping several shots into a man lying on the ground.
It all happened so fast, he said.
"I heard a loud bang. It just seemed like everything got kind of dark," he said.
"I realized I was just standing, looking down at this shadow."
Husbands said he doesn't remember bolting for the escalator as terror gripped the Eaton Centre food court.
"People were ducking and screaming. It didn't make sense to me," he said, his voice faltering at times.
He said he stumbled home in a daze.
When he got to his apartment, he said he turned on the television and learned there had been a shooting at the downtown mall.
"I just felt so sad," he said.
On the stand for a second day, Husbands said he had only gone to the Eaton Centre on that Saturday evening in June 2012 at his girlfriend's urging.
An attack that almost killed him several months earlier had left him paranoid and wary of crowds.
"I was still having nightmares. I was still having flashbacks," he told the jury.
The prosecution maintains Husbands, now 25, of Toronto, opened fire in a deliberate revenge shooting, killing two people and wounding five others.
The accused, who has pleaded not guilty to first-degree murder, denies that.
"I didn't want to kill anyone, so I didn't go looking for them."
Under questioning from his lawyer, Dirk Derstine, Husbands said he reluctantly went with his girlfriend to a mall sports store, where she bought ice skates and he bought roller blades and a jacket. They then headed to the busy food court to meet her mother for something to eat.
"I was agitated. I wanted to get out of there," he said.
The father of a six-year-old girl said he was carrying a gun — given to him by a friend a day earlier to look after — because it made him feel safer.
His unease, he testified, arose in February 2012, when a group of men attacked him and left him in a pool of blood.
He said he had no idea what prompted the stabbing but said he was convinced they had wanted to kill him and would try to finish the job.
"They'd do whatever they have to do to shut me up. I was worried for my life."
Among those who had taken part in that attack was Nixon Nirmalendran, 22, one of two men Husbands killed in the food court.
Husbands, who has convictions for drug dealing and sexually assaulting his child's mother, and Nirmalendran had known each other for years.
"At one point, Nixon was a very nice guy. He just went from getting bullied to not wanting to get bullied so bad that he became very aggressive," Husbands said.
"He just needed to let everyone know 'I have a gun and I can shoot that gun'."
At the mall that June evening, Husbands said his girlfriend was buying sushi when he looked up and saw Nirmalendran and his brother Nissan, who would be killed in an unrelated incident.
Nirmalendran, he said, urged his brother to shoot him and he saw Nissan reach into a pocket.
"I just felt like my arm was coming up," he said. And then the loud bang.
Husbands faces cross-examination on Wednesday.