Park Rangers keep telling tourists to Yellowstone National Park to be careful, that the animals, thermal features, and canyons are not risk-free, it's not a Disney facility. Sadly, some people don't pay attention as this Associated Press story for Yahoo News shows.
As a result, it is a rare year there aren't deaths in the park from wild animal encounters or falls. That said, all but a very few of the 3.2 million who visit each year leave with nothing worse than a mosquito bite or a sunburn, and vivid memories of a magical place.
The DrsC have taken houseguests to Yellowstone and Grand Teton National Parks at least every other summer for the last two decades. We've gone back ourselves nearly every year since 1973.
Loving those places is a major part of why we now call Wyoming home. If you come, please be careful and have a great time.