I'm not saying that you shouldn't shoot the dogs. I just think that the owner should be given the opportunity to contain the dog. Like I said before, if they care, they will take care of it. If they don't care, you will take care of it. Of course it won't be a secret who did it, just don't admit to it. Soon, you won't have any dogs running on your property. They will either be contained or dead. How can the owner blame you, if they are the ones who ultimately chose the dogs fate?
I know the season is short and your opportunities are limited. All I'm suggesting is give the owner one chance. And tell them, "this is your one chance".