He was lucky. I've heard stories of bears taking 6 rounds from a .357 mag and still having enough oomph to get a swipe and/or a bite in.

I've even heard that a Griz had enough energy stored in it's muscles and enough muscle/nervous system memory to continue mauling for up to 20 seconds after it's heart has stopped. I'm not sure if that's true of how you could prove it but it's interesting and scary all at the same time.