Cavalier or Pitball?

So my sweet little innocent Cavalier that gets a long with everyone has turned into a pitball. For some reason Sonny has decided to attack dogs in our neighborhood. This started a couple of months ago and he does this with everyone from a golden retriever to a little yorkie and we don't understand why. He runs up to the dogs and starts screaming and barking this awful sound that you think is him killing these dogs. Not only is it scary but it is embarrassing. At doggie daycare he is absolutely fine and he gets along with all the dogs so we don't what is going on. This is the last thing I wanted to have to worry and might be calling the Dog Whisperer here if things don't get better. Ugh!