A granddad lobbed more than two metres into the air by a charging bison has spoken of the horrifying incident from his hospital bed.

Carl Isom-McDaniel, 65, suffered multiple broken bones in the encounter in the US’s Yellowstone National Park last week.

Footage circulating widely online shows the bison becoming agitated and charging full tilt at Isom-McDaniel. He is chased through trees before he is eventually hooked on one of the animal’s horns and hurled into the air.

Isom-McDaniel’s injuries include four breaks to his femur, the strongest bone in the body.

The terrifying incident occurred when he was walking near a campground in the park with his 13-year-old grandson. The pair stopped to take a picture of the animal from about 100 metres away.

“We saw the bison and he was down, he wasn’t showing aggression or anything like that,” Isom-McDaniel said on Monday (local time) from his bed in a Montana hospital.

That changed in a blink. The 900-kilogram animal shifted its attention to Isom-McDaniel, chasing him around a tree before launching him into the air.

“They move faster than you could ever imagine,” he said.

“It picked a target. That target happened to be me.”

“He just kept coming and he was more aggressive and as soon as he got off that tree he launched me in the air.”

Carl Isom-McDaniel is tossed high into the air by the angry animal. Photo: AAP

After McDaniel hit the ground, photographer Mike MacLeod, who captured the encounter on video, had to step in, he told Cowboy State Daily.

“I was really afraid he was going to gore the guy on the ground, so I stopped videotaping and ran at the bison, yelled loud, and was trying to be as big and intimidating as possible,” MacLeod said.

Isom-McDaniel was taken to hospital, where he has been treated for multiple broken bones near his hip. He said he was grateful the outcome wasn’t worse.

“Even though I was on the ground, he could’ve stomped me, he could’ve gored me, he could’ve done anything,” he said.

ZooMontana assistant curator Allyson Welborn said McDaniel did nothing wrong but was “caught up in the wrong place at the wrong time”.

“Personally, I wouldn’t get out of my vehicle at all this time of year because obviously we saw what happens,” Welborn said. “He did everything right. He snapped that photo and kept on going.”

Bison rutting season in Yellowstone runs through the US summer, from June until about September.

The US National Park Service advises visitors to stay at least 100 metres away from from bears, wolves and cougars – and at least 20 metres from all other animals, including bison, America’s largest land animal, and elk.

“If an animal moves closer to you, back away to maintain a safe distance,” the park’s website says.

“It’s illegal to wilfully remain near or approach wildlife, including birds, within any distance that disturbs or displaces the animal.”

Yellowstone authorities have said the offending bison won’t be euthanised or relocated. Isom-McDaniel reportedly supports that decision, as does Welborn.

“Wild animals. We’re encroaching on their space in the national parks, so yeah, I’m happy he’s not being euthanised,” she said.