Andrew Mixemong, 59, died from his injuries after he was attacked behind Dino's deli in July of 2012.
Jessy Herlichka and Paul McClung are each charged with second-degree murder in Mixemong's death. Both of the accused are 29 years old. They have both pleaded not guilty to the charge.
Kelly Mortley testified in court Monday that Mixemong had tried to calm an escalating situation between Herlichka and McClung and the staff at the deli.
Mixemong's wife worked at the deli. The jury has previously heard that he had come to the business to pick her up.
Mortley testified that Herlichka told Mixemong he would show him trouble immediately before he struck him.
"Then he punched Andrew in the face so hard, when he hit the ground, I thought I would be looking at a smashed pumpkin," Mortley told the court.
That's when Mortley said she called 911.
The Crown contends Herlichka beat Mixemong to death. Mortley said McClung threatened her and her son, Randy, who tried to stop the attack.
In Mortley's 911 call, an unidentified male can be heard yelling in the background.
Several witnesses have testified that Herlichka appeared intoxicated.
The lawyers for the accused will have a chance to cross-examine Mortley in court on Tuesday.
The Crown is expected to wrap up its case early next week.
Click on the video to see a full report from the CBC's Michelle Cheung.