What if he had walked off track onto some molten lava?
I remember in Carlsbad Caverns years ago you could see where someone had left the paved walkway, walked over to look down into some pit in the caverns. I showed it to the ranger when he came by.
An acquaintance of ours said when she was little, and on her first trip to Yellowstone, a family stopped, one little boy jumped out, ran to a pool and jumped in. Instant screaming and death. When the rangers arrived they came with a net as his body had boiled and fell apart on retrieval.