1st of all, black bears attacks here in B.C., whether started as protection of cubs, territory or food, generally change to predatory. You become a food item. This is not heresay or guesswork, and was spelled out in no incertain terms in the "bear awareness" course ALL Provincial employees were in attendace for. Grizzlies, on the other hand, while not unknown to turn predatory, did so very much less often than black bears.
I shot 8 "trouble" bears one fall at work in Corrections. The bears were chasing the night shift outside Prowl officers who had some close calls. I shot 2 of then with my somewhat altered 1911. Both bears were in the 300 to 350 pound range, large for being town/garbage bears.
1st was a side head shot with a 230gr. FMJ = DRT. The range was close, about 10yards. I shot him(both were boars) when he turned his head as a car went past on the highway.
The second was at a range of about 15' as he was walking, pacing me as I was on the other side of the ecercise yard from him. He was parallelling me. I shot him with a 260gr. SpeerHP, loaded with W630powder, 11.9gr., Speer's max. frome my 5" Wilson barrel, they ran 960fps. The bullet entered the left side behind the elbow, double lunging him, just above the heart. He immediately coughed up blood, then bit at the entrance hole in his left side. He had stopped having interest in me. He just stood there, with his head down, then collapsed.
The other 6 bears were shot with rifles including a .30 wildcat I had made up on an 8x57 case with an '06 neck.
That one is a different story.