An excellent recent documentary was made about the grizzly attacks back in the 60's, with interviews of surviving victims as well as rescue
crew. It was inevitable due to the artificial feeding of bears as entertainment common in the Natl Parks during that era. But by far the most
dangerous animal in Yellowstone are bison bulls, not grizzlies; and statistically, by far the most fatalities in Glacier NP are due to drowning.
Those glacial streams are pretty vigorous, and careless snowmobiling is infamous for drowning incidents too, when those things cave into
frozen-over creeks and ditches.