It's advised to stay at least 25 yards away from Bison. Earl Hughes/YouTube

Video is circulating of a man petting a bison at Yellowstone National Park.

He puts his hand over the railing, and at one point the bison backs away.

It's unclear when the footage was shot.

According to USA Today, park officials are looking into it.

Last month, two people were injured by bison while visiting parks.

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A viral video shows a man petting a bison at Yellowstone National Park - and now the "illegal act" is being investigated, a park official told USA Today.

"The individual who recently was captured on video touching a wild bison along a park boardwalk showed an incredible lack of judgment and common sense," the statement said. "Not only did he put himself and others at risk, he violated regulations designed to keep these animals wild. We expect better from our visitors."

Park officials told USA Today that they are now investigating the incident. It is unclear when it took place, but the video was uploaded to YouTube on July 8.

In the video, the man, who has not been identified, reaches over the railing and pets the bison once. Upon a second attempt, the animal skittishly backs away.

As he approaches, you can hear a man off camera say "No, no, no. Don't do it, no." He does it (it being pet the bison) as a large crowd looks on.

The video was uploaded with the description, "what not to do."

It's advised to stay at least 25 yards away from bison, although the park's website says that "the animals in Yellowstone are wild and unpredictable, no matter how calm they appear to be. The safest (and often best) view of wildlife is from inside a car."

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In the past month, two people have been hurt by bison in parks.

On July 28, a 17-year-old tourist visiting Theodore Roosevelt National Park in North Dakota was injured by a bison that charged them from behind and sent them soaring through the air. Just before the tourist encountered the herd of bison, two had been fighting.

And on July 22, a bull bison tossed a 9-year-old girl in the air when it charged a group of tourists at Yellowstone National Park. Following the toss, the bison ran through a crowd of about 50 people surrounding the geyser Old Faithful.

The park spokesperson offered USA Today simple advice for close encounters with bison: "If need be, turn around and go the other way to avoid interacting with a wild animal in close proximity."

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