To keep dogs would also have hurt humans, because otherwise, they would have kept them, or sold them, or something.
According to the article, they couldn't afford to keep the dogs, so they tried to find homes for the dogs, but they didn't manage to, and then decided to kill them. They didn't kill the dogs because they would benefit from killing them, but because it would be expensive to keep them, and in a way, I think that this is something they should've thought of before they bought the dogs in the first place.
A little harsh for punishment suggestions, isn't it? I am unsure of the animal cruelty laws in Canada, but I would assume it would be at most a large fine with a few years in prison, and that is at the extreme itself. I would assume a fine would be the main punishment.
I'm not saying they should be punished as severely as if they had killed humans, and I apologize if this contradicts something I've said before, but I forget. They should have a punishment, though.