The bear seemed pretty close to done until it was re-energized by the eyeball infusion. So maybe: bear kills Surma, bear gets its eyeballs exorcised (by Seagull Mage?), bear collapses.
In case it's not obvious, I am still very much hoping that the Seagull Mage was a Chekhov's Gun, not just random color.
Also, a TPK is probably not necessary even if they fail to sneak. If they all scattered the bear might miss some.