I am an Attorney-at-Law, licensed to practice law only in the state of California. Unless we have both signed a formal retainer agreement, you are not my client, and my discussion of issues does not constitute legal advice. Opinions expressed herein are those of the author, and do not necessarily represent the opinions of those who hold other opinions.
Most, if not all, states have statutes addressing dangerous or nuisance dogs. A dog which left its own yard, entered a fenced yard and killed a domestic animal therein would almost certainly qualify for any action authorized under the statute - which is usually shooting the offending dog.
You can contact the OK and your county bar association for referrals if you really think you are the victim here.
The foregoing is for general information purposes and does not establish an attorney-client relationship.