Zhao Guang Yu's face is still bruised from the night four men attacked him and his wife in their Toronto convenience store last month, hitting them and stomping on his face as he was lying on the ground.It's painful for Xue Lin to hear her own bloodcurdling screams on video from a surveillance camera outside their store, as attackers allegedly pummelled her husband. Inside, Lin was shielding Yu with her body as the men battered him against the ice cream freezer, she says — but that didn't stop the men from beating her as well.Minutes earlier, Lin says, the couple had forced a combative customer out after she refused to wear a mask. The attackers came in apparent retribution, after the customer told the men she was "hit" for "no reason," according to the sound on the surveillance video.None of the altercation with the customer, or the attack by the four men, is visible on camera, but some of it can be heard on the audio.Lin says she felt helpless during the attack; her mind was blank, as she desperately tried to protect her husband."Four guys, tall guys," she said. "Of course we can't do anything."Lin and Yu have insisted all customers wear a mask since early in the COVID-19 pandemic, even before mass closures started in March. The couple own Levol Convenience Food Mart on Dundas Street West, just south of Kensington Market. They opened in 2016, and Lin says she always remembers her customers after they've been in a few times. She says she doesn't scare easily, even while working alone at night with customers who can sometimes get difficultBut after the incident, to avoid conflict, she says they keep the door to the shop locked at night, and only open it to people wearing a mask. Masks are critical, Lin says; her parents live downstairs, and she feels a responsibility to her family and customers' health.Most customers willingly wear their mask, or buy one for a dollar. But on a Thursday night in mid-April, Lin says, a woman refused to put her mask on despite repeated requests to wear it or leave. She was laughing with another woman in the aisles, mask in hand, she says.After asking several times, Lin says she finally grabbed the woman to pull her out of the store. The customer punched her in response, Lin says, also hitting her husband.Lin says she fought back, kicking as the couple pushed the fighting customer out. Outdoor security footage, supplied by Lin, captures a woman saying, "Don't touch me," and then daring them to strike her, saying: "Hit me," as Lin screams at her to get out (the people are out of sight in the video).Outside the store, a woman's voice says to to call somebody. A sobbing woman later tells a man that store workers "attacked me for no reason."That's when four men entered, Lin says — regular customers she recognized.To her shock, she says, they started hitting her husband.The audio captures a man yelling, "Why did you hit her?" and shouting before Lin starts shrieking. Her husband yells in apparent agony.A 'mountain' of bruisingThe men knocked store shelves down as they beat him, Lin says. Their blows knocked her husband to the floor, despite Lin hugging him to protect him.A man was stomping on his face while Yu was unable to move, she says, before they finally left.The next day Yu's face was black with bruises, with one eye "like a mountain," Lin says."My husband stayed home [for] two weeks," she said.'We're not fighting people'Toronto Police got a call around 9:30 p.m. on April 15, and continue to investigate a reported assault.Lin says she was crying as they talked to police, she was so worried about her husband. "I'm going to close my store," Lin says she thought after the attack, sleepless and devastated that night. She woke up with pain in her back and shoulders from the blows, but decided to open up later that day.Weeks later, Yu is also back to work, though he still has bruising on his face. He didn't want to see a doctor at the time because the hospital seemed too dangerous due to COVID-19, Lin says. But she worried about potential head injuries and exposure to COVID-19 during the assault.An attack like this has never happened before, says Lin: "We're not fighting people."Toronto Police say they have made no arrests in the case.'We don't want more people [to] get the virus'Lin says she and her husband can't have any tolerance for people who don't wear masks — even if it's meant losing business during the pandemic.It's more important to keep people safe, she says, and people need to respect their wishes."We don't want more people [to] get the virus," she said."I reduce business? Fine. I need to do my way."Lin notices more people taking precautions against COVID-19 in recent weeks, though some people still argue with the mandatory mask policy.Lin says there were two previous times that she had to grab people and call police when unmasked customers refused to leave. "We don't want fighting," said Lin, adding she usually tries to handle the situation herself before calling police."If you don't like to wear a mask ... you don't need to come in," said Lin, who sometimes fills simple orders for customers while they wait outside. They also offer free gloves for customers. "[It's] fair to other customers, fair to us."She urges people to take masks seriously."Right now... this weather is very hot," said Lin. "But still, think about health," she added."So, please wear [a] mask."