I would call the cops. If they are close by and the dog hasn't been in there long, I wouldn't resort to breaking the window. However, if it will take the cops over 5-10 minutes to arrive, I would find something like a rock and try to break open the window. First I would try the door, but if it didn't work i would definitely break the window. I wouldn't worry about having to pay for the window, either. If you report animal cruelty and say you were just helping the dog, they won't make you pay.