Carla Cheney told CBC News she hadn't yet started her shift and was in her own clothes outside the store with colleagues on Tuesday when she spotted a Walmart customer leaving his dog in a parked truck.
The dog jumped out of the open window twice to follow the man, Cheney said.
The man took his dog back to the truck and rolled up the windows, leaving them open about an inch, Cheney said. The man then headed into the Walmart.
'Told me it was none of my business'
"I said, 'Is this really happening? I'm going to give him about five or 10 minutes and then I'm going to call the police,'" Cheney recalled.
She called the police and an officer arrived to get the man's licence plate, then headed into the store to find him.
Later on, the man left the Walmart and got into his truck, Cheney said. Before he left the parking lot, he pulled up to the table where Cheney was sitting with her colleagues.
"He pulled up to us and said, 'Hello, ladies, how are you?' And I said, 'You shouldn't leave your dog in the car,'" Cheney said.
"He told me it was none of my business and I said that that was fine, that if I saw him do it again I would just call the police next time. He said he was no longer going to be shopping at that Walmart, and I said, 'OK.'"
Called to manager's office
Later on that day, Cheney was called into the office of her manager, who she had spoken to a week earlier about a dog in a hot car and was told there was nothing they could do.
She said she told him her side of the story about the dog in the truck and he told her to come to him with any problems in the future.
Cheney said she wouldn't do that.
"So I [told him] if I did see something unsafe, that I would just go to the police if I thought it was necessary," Cheney said.
"He told me then that I was terminated, he wanted my vest, my badge, and to clean out my locker and that I needed to leave."
'I thought I was doing the right thing'
Cheney also said that another former Walmart employee was scolded last week for confronting a customer about leaving a dog inside a vehicle. She said that person had already given his two weeks' notice, but that the manager sent him home and told him he'd be paid for the rest of the two weeks.
"Now I'm worried that other associates won't say anything and they'll be afraid that they'll lose their job if they do say something," Cheney said.
"[The manager said I was fired] because I was rude to a customer, but I felt because I was not even on the clock, it shouldn't have been an issue anyways. And I don't think it should be an issue even if I was on the clock … because it's on the news and we're being told not to leave animals and children in cars.
"I thought I was doing the right thing."
Cheney said that on the whole, Walmart is a good company, but thinks the Kemptville store needs to go over what staff are supposed to do when they see something unsafe in the parking lot.
In an emailed statement, Walmart Canada wouldn't comment on Cheney's case, but said it has guidelines that cover situations like the one Cheney faced and is reviewing them with staff in Kemptville and across the country.