I am sure you are familiar with the famous cartoon of the dog that always barked at the mailman and everyone else who came to the door, but never attacked. The dog's bark signals that something out of the ordinary is happening, but it doesn't predict what that something is. In the same way, when you hear a dog barking in the distance it's impossible to know whether the barking dog is a harmless dog or a dangerous dog, but you know you should certainly find out.