A rampaging bison in Yellowstone National Park hooked a man who was trying to run away from it, and then tossed him about eight feet into the air at a campground. The man, Carl Isom-McDaniel, who serves on several local community boards in Washington State, suffered multiple broken bones.

The attack occurred at about 8:30 on Friday night at Bridge Bay Campground near Yellowstone Lake, in the southeastern quadrant of the park, in Wyoming.

The visibly agitated bull bison was roaming the campground and charging at other groups of campers, as seen in a video taken by Mike MacLeod, a professional photographer based in Bozeman, Mont., about 130 miles away.

There were plenty of tourists milling around, with sunset still about an hour away, and the campground was populated with small recreational vehicles and tents.

Everyone was standing a distance away from the bison, which was most likely experiencing a surge of testosterone, as mating season is just beginning, Mr. MacLeod said in an interview on Sunday.

First the bison charged at a small group of teenage boys, who scattered, he said, before continuing to run around.

Then, the bull bison stopped, wallowing in dirt next to a campground road just a few feet away from a picnic table that still held dinner leftovers.

“When he got up, it was kicking like a rodeo horse who’s clearly very agitated,” said Mr. MacLeod, a former combat photographer who also has a degree in wildlife biology.

At that moment, a pickup truck drove by, and a man with a long white beard and his grandson stopped to take photos of the bison, he said. (Bison can weigh up to 2,000 pounds and, despite their prodigious size, sprint up to 30 miles an hour.)

“The bison stopped rolling in the dust and kind of sat up. He’s looking in the direction of those two,” he said. “And as soon as they stop taking pictures, the bison stands up and the grandfather’s like, ‘Let’s get out of here. I don’t like this,’” Mr. MacLeod said. Then another pickup truck passes.

It appeared to onlookers that the bison had targeted the truck, he said. But once the truck drove away, the bison started chasing them around a cluster of pine trees. The grandson was able to dart away, Mr. MacLeod said, but the bison caught up to the grandfather, hooking him with its left horn near the hip before flipping him.

“I knew he was in danger because the bison didn’t leave,” he said. “He stood right over Carl, and he was really, really angry. His head’s pumping up and down and he displayed all that aggressive behavior.”

“I put my camera down, and I ran at the bison pumping my arms up and down, yelling at the top of my lungs and jumping up trying to look big and distracting.”

Others followed, and Mr. MacLeod said the rushing crowd most likely caused the bison to turn and run away. Other campers took care of Mr. McDaniel, who serves on several local boards and commissions in his community in Whatcom County, until a park ambulance arrived in about 10 minutes.

“He was in a lot of pain with his leg, and otherwise he was conscious the whole time, in good spirits, joking,” Mr. MacLeod said.

Neither the National Park Service nor Yellowstone officials have released any information about the attack. A hospital did not immediately respond to a request for an update on Mr. McDaniel’s condition.

The start of mating season for the bison coincides with the beginning of the peak of Yellowstone’s summer tourism season. Park regulations require visitors to stay at least 25 yards, or about 75 feet, away from bison at all times.

Mr. MacLeod said everyone he observed on Friday remained a “respectful distance.” But upon leaving the park this weekend, he said he noticed “half a dozen far more dangerous instances where people were way closer and being aggressive.

“Most people see that these two did not ask for it,” he said.