You called the cops and knew they were coming. Of course, the dog will get excited when a cop car pulls up, lights flashing, strangers getting out. Tie up the poor dog or leave him in the house.
Everybody should know by now to expect that kind of behavior from the police. I happens many times every month. If you take a calculated risk dialing them for help, lock up securely all that is near and dear to you. Expect it!! That we cannot explain this attitude adjustment does not matter in the least.