The same thing happened today!
Or would have: A hawk had a squirrel pinned down in our yard and the dog got all excited by the four of us jabbering and pointing. Naturally, she wanted out. My wife was afraid for the dog's safety as the hawk was really big and our dog is a Cavalier King Charles Spaniel (A breed of small, weak and fairly unintelligent dogs). I let her out anyway and she dashed toward the raptor with either no fear, or more likely--no sense.
The hawk, which had its back to the onrushing dog, was startled and flew away without its lunch. The squirrel was still alive and had wit enough to run up a nearby tree. The dog kept its record of never killing a mammal (she is an insect mass-murderer) though not from lack of trying. As it was, she was very excited and ran around the yard for some time after the incident.
The bird did not go far. It alighted in a tree about 100 feet away and stared at the dog in a menacing way. I am not sure that carnivorous birds can stare in a non-menacing way, so perhaps I shouldn't take too much from this. I imagine though, that the hawk was sizing up our little dog as potential prey.