Vacationer Hailey Dayton, 18, who filmed the incident while observing the animals from a safe distance, says people were getting dangerously close to the bison.
‘My brother and I were looking at the hot springs, and we saw a bunch of people running down the path to the bridge. We saw through the trees some people petting the bison, super close,’ she told NBC.
‘Because it was agitated by all the people and noise, it just kind of attacked. After that, everyone was screaming. There were a bunch of kids crying.’
Social media has been deluged with people attacking the group of tourists for getting so close, and singling out the child's parents in particular. Their whereabouts at the time of the incident is unknown, but vision shows tourists scattering in all directions as the animal charged - the young girl apparently left to fend for herself in the panic.
People are repeatedly warned to stay at least 75 feet away from the animals at all times. Although the creatures may appear relatively tame, they can be unpredictable and will charge suddenly if they feel boxed in, surprised or threatened.
Bull bison can weigh up to 910 kilos and may charge at 30 miles per hour.