This is a fascinating story.  A previous comment compared these bears to our NA black bear.  They appear to be about the same size.  However, I have a fair bit of experience bear hunting, and I don't think that the black bear has been born that would charge under these circumstances.  In fact, having messed with grizzlies as well, I would say that it would be a pretty slim chance that you would be charged by a remaining grizzly after having just dumped one of a pair.  It seems that the bear that Mr. Rahman hunted were born with an attitude! 
The one caveat I would make to my comment would be to those of you hunting Prince William Sound, beware of the brownies on Hinchinbrook Island!  These are a mean bunch of bruins!  Local rumor is that it was the dumping ground for problem bears for years, resulting in a particularly mean strain.  I don't know if this is true or not, but the attitude of these rascals is undeniable!