THIS is the terrifying moment a hippopotamus drags a zebra to its death ? the first time an attack has been caught on film.A BBC1 crew captured the incident and recorded the enormous hippo ripping its helpless prey apart with its massive jaws.David Breed, a wildlife guide working with the crew in Kenya, said: 的ve only seen hippos kill wildebeest at river crossings five times in 20 years. I have h