A bull bison at Yellowstone National Park tosses an unidentified grandfather about eight feet during a charge near Bridge Bay Campground, and witnesses drive the animal off while emergency crews treat the man for serious hip and leg pain.Photographer Mike MacLeod recorded the bison as it charged a group of children, chased a passing white truck and then attacked the man who was walking with his young grandson, who escaped unharmed.Park officials say bison injure more people at Yellowstone than any other animal, note the strike comes during the rut season and remind visitors to keep at least 25 meters from large animals and 100 meters from bears, wolves and cougars.