A jogger killed a mountain lion with his bare hands after the animal attacked him on a trail in the foothills of the Rockies.
The runner heard the wild cat behind him and, as he turned, it pounced and began savaging him, pouncing at his head, and clawing and biting his face and arms.
He managed to fend it off with his forearms and then jumped on top of the animal, somehow managing to suffocate it.
The man, who has not been identified, suffered bites to his face, arms, legs and back.
But he was still able to hike to hospital, where he was being treated for serious, non-life threatening injuries.
The attack happened on the west ridge of Horsetooth Mountain, a park 66 miles northwest of Denver, Colorado.
Rebecca Ferrell, spokeswoman for Colorado Parks and Wildlife, said: "It’s an amazing story. Everyone is baffled and impressed. He had no weapons, no knives or trekking poles with him. How did he do it?"
The body of the mountain lion was found at the scene and was described as a "juvenile" thought to have weighed about 80lbs.
It was being tested to see if it was rabid, and the victim was being treated for any possible infections.
Experts initially questioned how the man could have got the better of the mountain lion after the surprise attack.
But a necropsy later confirmed suffocation as the cause of the animal's death.
A spokesman for Colorado Parks and Wildlife said: "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."
He added: "The runner described hearing something behind him on the trail and was attacked by a mountain lion as he turned around to investigate.
"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. He was able to suffocate the animal while defending himself from the attack."
The encounter happened in a 2,711-acre park which has an elevation of between 5,430ft and 7,255ft, and 29 miles of hiking and cycling trails.
Mark Leslie, a parks manager in Colorado, said: "The runner did everything he could to save his life. In the event of a lion attack you need to do anything in your power to fight back, just as this gentleman did."
Adult mountain lions, also known as pumas or cougars, can grow to 220lbs. Attacks are uncommon in Colorado. There have been three deaths and 16 injuries in the state in the last 30 years.
In 2016 a mother successfully rescued her five-year-old son after he was attacked by a mountain lion near Aspen, Colorado.
Across the United States fewer than 20 people have been killed by mountain lions in the past 100 years.
Most attacks have been recorded in California. In 2012 a mountain lion was shot after wandering into the downtown area of Santa Monica, California.
Wildlife officials in Colorado later said the man choked the animal to death, and had succeeded through "sheer will". He is expected to make a full recovery.
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