The Crown, however, said Christopher Husbands, 25, who has pleaded not guilty to two counts of first-degree murder, did indeed plan to kill his victims.
"There was only one shooter, there was only one person seen with a firearm," prosecutor Mary Humphrey told court in her opening statement.
"There was only one person that inflicted all the casualties, physical and emotional, and that was Christopher Husbands."
However, defence lawyer Dirk Derstine will argue the accused was indeed responsible for the deaths and injuries but that it was a "chance encounter" with a group of five men that prompted him to open fire, the judge said.
Husbands, in jacket and tie, sat quietly as he watched proceedings attentively.
He is also charged with five counts of aggravated assault, one of criminal negligence causing bodily harm, and one of recklessly discharging a firearm. He has pleaded not guilty to those charges as well.
The evening attack in June 2012 prompted hundreds of people to flee in terror. A pregnant woman was trampled in the mayhem. A 13-year-old boy was shot in the head, but survived.
The trial before Ontario Superior Court Justice Eugene Ewaschuk opened with Humphrey outlining the case against Husbands, who she said went to the mall with a fully loaded handgun and opened fire after a group of five people walked past him.
Humphrey told the court there was no argument prior to the shooting, but that Husbands said "What's up" possibly followed by a vulgar term.
"He pulled out his gun and emptied 14 rounds towards his targets."
The gunfire killed Ahmed Hassan, 24, and left Nixon Nirmalendran, 22, fatally injured.
Surveillance video screened for the court shows Husbands continuing to shoot at Nirmalendran as he lay on the ground before turning and running away.
Husbands turned himself into police two days after the rampage that shocked the city.
According to the prosecution, the shooting was the result of bad blood between Husbands and Nirmalendran and friends.
The animosity stemmed from an incident several months earlier in which several men stabbed and robbed Husbands at an east-end home.
What prompted that attack is not clear, but it may have been because Husbands was sleeping with a friend's mother, a drug deal gone sour, or he had offended someone, court heard.
The evidentiary phase of the trial began with a Toronto police detective, who collected video showing the shooting and ensuing pandemonium.
One of the three surviving members of the group at which Husbands fired will also be testifying, court heard.
The trial resumes on Tuesday.