A bull bison tossed a man nearly eight feet into the air in the United States’ Yellowstone National Park on Friday, seriously injuring him, according to an eyewitness who filmed the attack.The incident occurred at the Bridge Bay Campground while the victim and his grandson were taking an evening walk. Photographer Mike MacLeod, who was camping nearby, said the pair had kept a good distance from the animal before it suddenly attacked.A video circulating on social media also shows the bison running around and eventually targeting the man and throwing him into the air.McLeod said the bull was already moving aggressively into the campground, causing several visitors to scatter, before it ultimately targeted two hikers. “They were walking down the road a fair distance from the bison and it started running at them,” he said, as quoted by local news outlet Cowboy State Daily.The grandson escaped unharmed, but the old man was chased to a group of trees before the animal could catch him.According to MacLeod, the bison attacked the man with one of its horns, throwing him into the air, before falling hard on his side.The witness said the animal then remained close to the injured man, leading to fear that it might attack again. “I was really scared he was going to knock that guy to the ground,” MacLeod said. He said he and several onlookers ran toward the bison screaming and eventually chased it away.Emergency responders arrived a short time later and took the injured man for treatment. Although there were no obvious external wounds, MacLeod said the victim complained of severe pain in his hip and leg. Later, the man’s grandson informed them that his grandfather had suffered “quite serious injuries” and was in critical condition.MacLeod said the attack was special because, unlike many wildlife encounters in Yellowstone, visitors had behaved responsibly. “I didn’t see anyone coming close,” he said. “People … kept their distance. They were very respectful.”He described the bull as unusually aggressive and said that before attacking the victim, it attacked several people and even a pickup truck passing by.The attack occurred during Yellowstone’s annual bison mating season, or rut, which lasts from June to September. During this period, male bison become more territorial and aggressive as they compete for mates.The incident is the second bison attack on a visitor to Yellowstone this year. A 12-year-old boy was injured in a separate encounter near the park’s mud volcano area in June.