Similar thing happened to my family.
We own 5 malamutes, all really pack oriented. Neighbors never have a fence, just let their dog run and poop in anyone's yard. Long story short neighbor kicks dog out to potty and it runs in our house as we are unloading the car. Little terrier meet large malamute.
The crazy neighbor lady tried to take us to court but no one would hear of it. Then she tried to get everyone in the neighborhood to sign a petition saying we'd euthanize our dog. That didn't happen either. Finally she demanded $2,000 to replace the pure bred, show dog for which no one could find any papers. She didn't get that either (although we did buy her a leash and collar).
Anyway, the jist of what we learned from cops/animal control is that as long as your animal is on your property, it's not your fault. You will want to tell them immediately though.