A man running on a popular park trail in the mountains of northern Colorado killed a mountain lion after it pounced on him from behind.
Colorado Parks and Wildlife (CPW) officials say the man sustained serious injuries after he was bitten on his face and wrist by the young male lion.
The man, who has not been named, turned after hearing a noise behind him, just as the lion lunged, officials say.
The cat died from suffocation, state wildlife officials have determined.
Monday afternoon's attack occurred on the West Ridge Trail at Horsetooth Mountain Open Space near the city of Fort Collins - about 66 miles (106km) from Denver.
The victim "described hearing something behind him on the trail and was attacked by a mountain lion as he turned around to investigate," according to an official statement.
"The lion lunged at the runner, biting his face and wrist. He was able to fight and break free from the lion, killing the lion in self-defence."
After killing the predator, the man was able to leave the park on his own and call for help.
In a statement, officials described the wounds to his face, wrist, arms, legs and back as "serious, but non-life threatening".
After additional investigation, including examination of the lion, we have confirmed the victim's account that he was able to suffocate the animal while defending himself from the attack.— CPW NE Region (@CPW_NE) February 5, 2019
Officials later found the dead lion, which was determined to be a juvenile male weighing around 80lbs (36kg).
"The runner did everything he could to save his life," said Mark Leslie, CPW's Northeast Region manager, who did not say exactly how the runner killed the animal.
"In the event of a lion attack, you need to do anything in your power to fight back just as this gentleman did."
A reminder that living in Colorado means living among our wildlife. Our website has several great resources, including brochures about how to live and recreate with a variety of species. See our Living with Lions brochure for more information: https://t.co/9t0vPivxdz pic.twitter.com/NvoP9C3pUE— CPW NE Region (@CPW_NE) February 5, 2019
Cougars, also known as mountain lions, panthers or pumas, are members of the wild cat family. They live across the Americas, from British Columbia to Argentina.
Mountain lion attacks in North America are very rare, officials say - CPW says fewer than a dozen people have been killed in more than a century.
Instances of attacks are often seen among sick or starving lions, which normally are elusive and tend to avoid humans. The animal in Monday's attack has been taken to a nearby lab for a post-mortem examination to be performed.
If you ever see a big cat, authorities say not to run, since that may trigger the lion's hunting reflexes.
"Running may stimulate a lion's instinct to chase and attack," the park service said.
Instead people should stand firm and make an effort to look larger, and if attacked, fight back using any weapon at hand.
"What you want to do is convince the lion you are not prey and that you may in fact be a danger to the lion," officials said in a statement.
"People have fought back with rocks, sticks, caps or jackets, garden tools and their bare hands successfully," the park statement read, adding that sensitive areas such as the eyes should be targeted first.
Last May, one cyclist was killed and another injured by what authorities described as an "emaciated" cougar in Washington state.
In September 2018, a hiker in Oregon was found dead in what officials suspect was the state's first ever fatality caused by a wild mountain lion.