A nine-year-old girl was charged and injured by a bull bison at Yellowstone National Park on Monday.
Video of the incident, posted on social media, shows the animal throwing the girl high into the air.
She was treated by medical staff in the US park before being released, officials say.
Witnesses say the bison was surrounded by a group of 50 visitors, far closer than the recommended distance away, for about 20 minutes before it charged.
In a statement, Yellowstone Park officials blamed the proximity of the group for the bison charging.
They also reiterated official advice to stay 70ft (23m) from all large animals in the park - including bison, deer and moose.
The park, which is mostly in the state of Wyoming, also tells visitors to keep at least 300ft away from any bears and wolves they see.
Official advice says wild animals in the park should never be fed or approached by visitors.
"Wildlife in Yellowstone National Park are wild," they said in a statement. "When an animal is near a trail, boardwalk, parking lot, or in a developed area, give it space."
"If need be, turn around and go the other way to avoid interacting with a wild animal in close proximity," the statement added.
The video of the attack shows two people running away as the animal approaches.
Before the original 12-second clip was deleted from Twitter, the video had amassed millions of views and about 38,000 retweets, the Washington Post reports.
Details of the girl's injuries have not been made public, but park officials say she is from Odessa, Florida.
The statement says no citations have yet been issued to the family, but the incident is still under investigation.
Yellowstone is home to the largest collection of bison on public land in the US.
The animals are the largest land-dwelling mammals in North America, and can weigh up to 2,000lb (900kg).
Yellowstone officials say bison can run up to 30mph (50km/h) and are the animal responsible for the most amount of injuries within the park.