The park is home to grizzly and black bears, both of which are a top draw for the more than 4 million tourists who visit each year. It’s not clear whether the bear that attacked the boy was a grizzly or a black bear.
Yellowstone averages about one bear attack on a human per year, but it’s been three years since the last attack within in park boundaries, according to officials.
The family of four was hiking along the Divide Trail southeast of Old Faithful when the bear charged from the vegetation, chased the boy and knocked him to the ground, park officials said in the statement.
It wasn’t immediately clear what caused the bear to charge.
The boy’s parents deployed bear spray about 5 feet (1 ½ meters) from the bear’s head, causing it to leave. The family walked to the trailhead and drove to the ranger station at Old Faithful, where they were sent to a nearby clinic.
He was then transferred to a hospital in Big Sky.
Wildlife and law enforcement officials are investigating the attack and looking for signs that would identify the type of bear involved.