That dog should be under mandatory quarantine. At least for 10 days. Since the owner cannot control their dog, they will end up having to register it as “dangerous”. (This will be ordered by the court). The owner will have to formally register the dog as a dangerous animal, post signs on their property, muzzle the dog and keep in on a lead of no more than 3 feet when off property, notify the sheriff and animal control whenever it is loose, if outside and on property, the dog must be contained by a six foot fence. They may require it’s assessed by a animal behaviorist and undergo mandatory training. However, if that dog is on your property, without being under the control of its owner, you are 100% within your right to dispatch the animal. I’m sorry you’re going through this. I hope it all works out for you.