A grandfather flipped 8ft in the air by a bull bison at Yellowstone national park recently has spoken out for the first time about the encounter that broke his femur in four places, saying he believes the animal spared his life by choosing not to gore him.

The entire incident, he said, “was not as catastrophic as it could have been”.

Carl McDaniel, 65, gave an account of his sobering run-in with nature in an interview with CNN on Monday, one day after surgery to reset his broken leg, and amid hospital treatment for other injuries including severe bruising.

“We were about 100 yards away,” McDaniel, who lives in Washington state, said of the moment he and his 13-year-old grandson spotted the bison during an after-dinner walk at the Bridge Bay campsite in the Wyoming park on Friday.

McDaniel said the bison did not appear as if he was aggressive from his vantage point. “He was not having problems, and we took some pictures and decided to walk on,” McDaniel remarked.

Then, McDaniel said, the animal charged at them. His grandson was not hurt. But in an episode captured on video by a nearby photographer and viewed on YouTube by more than 1.1 million users, the bison estimated at 2,000lb (900kg) chased down McDaniel and flipped him into the air with its horned head.

“There was little time to decide what to do,” he said. “At that point, he was within 100 yards; he could be to us in seconds, so I told my grandson to run in one direction and I went the other to try [to] draw him away.

“When I was on the ground immobile, unable to move, he was right on top of me. He could have stomped on me; he could have gored me; he could have done almost anything to take my life – and he did not do so.”

A group of campers, including the photographer, Mike MacLeod, quickly descended on the scene, shouting and clapping their hands to scare the animal away and allow McDaniel to receive first aid.

“All the people that were there were amazing,” McDaniel told CNN. “They were all positive – they were trying to help as best they could.”

Emergency personnel responded quickly, the US National Park Service (NPS) said in a statement, and took him to a local hospital. Medical staff there made the decision to transport him to another facility in Bozeman, Montana, requiring a two-hour ambulance ride during which McDaniel said he was in intense pain.

He said he was strong enough to be able to stand on Monday, one day after his surgery – but now faces a lengthy recovery period.

“I will be doing physical therapy for the next few days to get to walk, but it was not as catastrophic as it could have been,” he said.

MacLeod had a slightly different take on the episode, describing the animal as “agitated, pissed off and charging anything and everything” in a vivid account of the episode published on Saturday by the Cowboy State Daily.

“I was just trying to get some dramatic footage of that bison having a fit,” he said, adding that McDaniel and his grandson were a “respectful distance” from the animal and had not done anything to cause it to charge.

On providing assistance to McDaniel, MacLeod told the New York Times on Sunday: “He was in a lot of pain with his leg, and otherwise he was conscious the whole time, in good spirits, joking.”

McDaniel serves on a number of community boards near his home in Kendall, Washington state’s Cascadia Daily News reported. He told CNN he and his grandson visited Yellowstone every summer to spend time together.

Bison rutting – or mating – season in Yellowstone runs from June until about September. The NPS statement about the bison attack that McDaniel survived did not state if the animal may have been aggressive because it was navigating the heart of rutting season.

“There are no further details to share,” the statement said.