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The mountain lion killed in Colorado by a runner who said he was in life-and-death struggle was an orphaned kitten, state wildlife officials said on Friday.

The big cat that attacked Travis Kauffman in Fort Collins on Feb. 4 was a male, between 4 and 5 months old, based on an examination of the animal's teeth, a necropsy performed by Colorado Parks and Wildlife veterinarians found.

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At the time of the attack, it probably weighed between 35 and 40 pounds, the veterinarians found. By the time of the necropsy, the mountain lion's remains were only 24 pounds, because it was partially eaten — most likely by its two surviving siblings, Colorado Parks and Wildlife spokesman Jason Clay said.

The attacking mountain lion and its siblings were probably without their mother, who is typically the sole caretaker, Clay said. The dead lion's two siblings were trapped following the attack and are now at a wildlife rehabilitation center with plans to release them back into the wild.

"Mountain lions are solitary animals, only coming together for breeding," Clay told NBC News on Friday. "We had no signs of an adult female being anywhere near the scene that day, or in the following days, which is one reason why we think these kittens were orphaned."

Kauffman, 31, was running on a scenic trail on Horsetooth Mountain when the young mountain lion lunged at him. The wounded Kauffman said he couldn't force the animal off of him, leaving him no choice but to wrestle it down and eventually step on its throat to kill it.

"Necropsy findings supported the description of events given by the victim," according to state findings. "The cause of death was determined to be multi-factorial including blunt trauma and strangulation."

The mountain lion killed by Kauffman "was hungry but not starving" and "rabies testing was negative," the necropsy found.