63 year old killed by mama grizzly in Yellowstone

We were camping a couple of miles from where this happened. We had heard that he was an experienced backcountry hiker so we couldn't understand why he wasn't prepared; he was hiking alone and without bear spray. We talked with a couple of park rangers and they couldn't give any better explanation than sometimes people who know better just get complacent. Elephant Back is a very popular hiking trail.