I disagree even with the 'attack as long as it's living.' Watch a cat going nuts through a bunch of mice. Smack smack smack...
I figure most animals will, in the face of multiple threats, possibly not even focus on one target if several are adjacent. And once a creature is prone and not moving, I expect some animals will move on to clear dangers (as far as the animal sees it).
I also typically have animals go for the tallest, loudest attacker, since they are obviously the big threat, or pick off the smallest/quiest one, in the hopes of peeling off the weaker members of the human 'pack.'