Bridge Bay Campground turned chaotic Friday evening when a bull bison hooked a man in the hip and flipped him about 8 feet into the air, leaving him with significant injuries, according to witness Mike MacLeod.
At least 100 yards had separated the pair from the animal when it suddenly charged again; MacLeod said the man and his grandson had been walking away after the bison appeared to calm down.
MacLeod and other bystanders rushed the animal after it stood over the fallen man, driving it off before EMS arrived; the grandson later said his grandfather was "not out of the woods yet."
The National Park Service has not released details, but MacLeod said campers had kept their distance and the bull appeared broadly aggressive during Yellowstone's June-to-September rut.
This was Yellowstone's second human-bison incident of 2026, after a 12-year-old was injured near Mud Volcano on June 26.