Before watching the video, the word that came to mind was "feral". However, upon watching it, that's not accurate or fair to wild creatures. Most animal species don't spontaneously assault their pack/tribe mates.
The motion speed and running time suggest to me the whole event ran perhaps 10 seconds, with the victim in no alert posture. No audio, but there is no appearance of provocation. The violence of it puts me in mind of A Clockwork Orange, but with greater rage.