Lorraine Ashkanese told the court her husband, 59-year-old Andrew Mixemong, had come to pick her up at the deli where she worked, in Midland, Ont., on July 6, 2012.
She said she was confronted by a bare-chested man while locking up.
"I thought he was drunk. I smelled beer. Just from his behaviour, the whole situation wasn't normal," she told the court.
Ashkanese said she asked her husband to speak the man. The next thing she knew, Mixemong was lying on the ground.
One of the accused, Jessy Herlichka, "just proceeded to pummel Andrew in his face, his nose, his eyes," according to Ashkanese.
"I pounded on Mr. Herlichka's back a few times to try to get him to stop."
Photos submitted in evidence show Mixemong with his injuries in hospital, where he later died.
Herlichka and Paul McClung, both 29, have been charged with second-degree murder.
McClung has pleaded not guilty.
At the beginning of the trial Herlichka pleaded guilty to manslaughter but the Crown rejected that plea.
Mixemong's brothers and sisters say they know there's more disturbing testimony to come in this trial, which is expected to last another three weeks.
"My brother was like a twin to me and part of me is missing now. I have to live with that. It never goes away never. I have to relive it all the time," his brother, Wayne Mixemong, told CBC News outside the court.