A tourist has been rushed to hospital after a massive bison tossed him eight feet into the air during a brutal attack at Yellowstone National Park.
The violent encounter unravelled at Bridge Bay Campground in Wyoming on Saturday when the bull charged at the man and drove its left horn into his hip before flipping him skyward.
Dramatic footage showed the victim, an older man wearing blue dungarees, being catapulted by the massive animal.
The bison - the largest land mammal in North America - had wandered into the campsite and grown increasingly hostile before launching its attack.
Bystanders rushed to assist the seriously injured man while others attempted to drive the animal away by shouting and charging towards it.
The grandfather had been walking through the campground with his young grandson when they came face-to-face with the restless beast, which had been giving itself a dust bath moments earlier.
The animal is said to have entered the area appearing angry and was charging at anything in its path, including a group of children who had been photographing it from what they believed was a safe distance.
When the bull turned its attention towards the pair, they tried in vain to seek shelter behind a small cluster of pine trees.
A tourist was rushed to hospital after a massive bison tossed him eight feet into the air
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While the grandson managed to escape without injury, the older man found himself desperately trying to evade the pursuing animal.
The bison closed the distance rapidly before driving its horn into the victim and hurling him into the air.
"I was just trying to get some dramatic footage of that bison having a fit. I would not have predicted that happening," Mike MacLeod, a former Army combat photographer, told Cowboy State Daily.
He added: "The bison hooked him with his left horn on his hip and tossed him in the air. He made a perfect flip and landed on his side.
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The tourist was with his grandson at the time of the horror incident
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"The bison was at least 6ft tall, and [the victim] was several feet above him."
The photographer and other witnesses helped frighten the animal away before emergency services arrived to provide medical assistance.
The victim was subsequently transported to hospital after being seriously injured.
Mr MacLeod said the man's grandson described the injuries as "pretty significant", adding his grandfather was "not out of the woods yet".
The weekend's horror is the second bison-related incident at the 2.2 million-acre national park this year, following an attack last month when a 12-year-old child was injured north of Fishing Bridge.
The animals are famous for their unpredictable nature, and are capable of running at speeds three times faster than humans.
During this period of the year, male bison experience elevated testosterone levels, which makes them particularly volatile and territorial.
The National Park Service has advised visitors to maintain a distance of at least 25 yards from the creatures at all times.
If confronted by a bison, people should avoid making eye contact and continue moving away from the animal.