Tell me it wasn't a 9mm.
Don't they usually advise that, if you going to carry a handgun in bear country, it be a minimum of 44 mag. or more?
Hey! Don't knock the 9MM. There's nothing wrong with it that an extra 3mm and a few grains of powder won't fix.
12 gauge with slugs.
From the Remington ballistics table:
9mm Parabellum muzzle energy is approx 350 ftlbs x 11 rounds = 3850 ftlbs.
40 S&W muzzle energy is approx 450 ftlbs x 11 rounds = 4950 ftlbs
45 Auto muzzle energy is approx 450 ftlbs x 11 rounds = 4950 ftlbs
3" 12 ga rifled slug muzzle energy = 3000 ftlbs.
Assuming the bears never had experience with hunters or firearms discharge they probably thought all humans were cute and tasty just like the two greens thay just ate. Once the warden began firing his handgun at point blank range, the bear probably didn't associate the noise and shock with the nearby humans.
As shown above, the accumulated energy delivered by 11 rounds of even 9mm at point blank range is pretty significant. Of course having colleagues nearby armed with shotguns probably gave the warden a measure of reassurance as well.
When my brother's USAF fighter squadron went to Alaska for training, they issued him and the other aviators 38 caliber sidearms in case they had to bail out in the wildness.
One of the aviators asked the leader if the 38 could be used on a grizzly bear. The leader said, "Yeah, it will annoy him so that he will kill you faster."