I witnessed one........but not on a human being; on our chihuahua we had with us when my family stopped to visit at the home of some distant relative (on my mother's side..............figures). I'm a kid at the time, ya see, and we pull up to the house of these old folks. Have the chihuahua with us (we were in the process of a cross-country move, so had the dog along), and we get out of the car with me holding his leash. The visitees open the front door, and out bounds the BIGGEST St. Bernard you have EVER seen in your life (found out later that they fed him a whole chicken every day). Just HUGE. You could literally ride this guy using a saddle. He sees the chihuahua......looking like a tasty little morsel, I guess.......and just pounces. To his credit, Chico the chihuahua bared his fangs, snarled, and decided to give it a scrap.
So here I am holding onto the leash of a little chihuahua while the Largest Dog on the Planet decides to attack him. People screaming, arms waving, lots of "Stop! Stop!", yada yada. All I could think to do was yank that leash for all I was worth to extricate the chihuahua from the brouhaha.
It worked, thank God. Little sucker practically flew threw the air and I caught him; got him away from The Monster from Hell.
No harm done, but poor little dude was shaking for hours. Couldn't help but think what it would be like to have that bruiser attacking a person; ugly doesn't cover it.
Of course, there was always this St. Bernard:
