In one instance, park officials were forced to put down a bison calf because of an encounter with a park visitor, CNN reported. According to Yellowstone, bison are vital to the park's ecosystem.

She said it was about 7:15 p.m., very foggy and "really eerie and mysterious" when they spotted animal prints. "There were bear tracks and bison tracks and we were taking pictures of those.

A bison dies in front of horrified tourists when it falls into a hot spring at Yellowstone National Park. USA Today “I thought it was a great photo opportunity.” ...

A bison was gruesomely boiled to death in a Yellowstone National Park hot spring last week — as tourists watched in horror. The buffalo met its ghastly end when it apparently stumbled into the ...

She said it was about 7:15 p.m., very foggy and "really eerie and mysterious" when they spotted animal prints. "There were bear tracks and bison tracks and we were taking pictures of those.