An eight-year-old boy in Colorado suffered "serious" injuries Wednesday night after a mountain lion bit him on the head in his backyard, officials said.

The unnamed boy was playing with his brother on a trampoline around 7:30 p.m. at their home in Bailey, about 47 miles southwest of Denver, when the boy ran to a neighboring house to visit a friend, Colorado Parks and Wildlife (CPW) said in a statement Thursday. As the boy ran across the yard, a mountain lion attacked and pinned the boy to the ground.

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“The kid was running and it probably triggered the lion’s natural response to a prey animal running,” Area Wildlife Manager Mark Lamb said. “We all hope that the child will be all right and you just hate to see this occur."

The boy’s brother ran into the house to alert their father, who ran outside and scared the mountain lion away, officials said. The boy was rushed to a hospital with serious injuries. He remained in the hospital overnight.

The mountain lion was described as “of smaller size,” officials said. It was unclear whether it was male or female.

CPW workers said they set up a cage trap for the animal and searched the area for about two hours with a team of dogs but were unable to track the mountain lion. The pursuit was expected to continue Thursday.

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Any wildlife that attacks a human must be put down for the public’s safety, according to wildlife policy in the state.

There have been three mountain lion attacks on humans this year, CPW said. Since 1990, there have been 22 attacks, with three of them resulting in deaths.