BILLINGS, Mont. - A Colorado man used a chain saw to fight off an apparently starving mountain lion that attacked him during a camping trip in northwestern Wyoming with his wife and two toddlers.

Dustin Britton, a 32-year-old mechanic and ex-Marine from Windsor, Colo., said he was alone cutting firewood about 100 feet from his campsite in the Shoshone National Forest when he saw the 100-pound lion staring at him from some bushes.

The 6-foot-tall, 170-pound Britton said he raised his 18-inch chain saw and met the lion head-on as it pounced - a collision he described as feeling like a grown man running directly into him.

"It batted me three or four times with its front paws and as quick as I hit it with that saw it just turned away," he said in a telephone interview with The Associated Press.

Wildlife officials said Sunday evening's attack about 27 miles west of Cody was highly unusual because mountain lions are reclusive by nature. Only eight cases of mountain lions acting aggressively toward humans have been documented in Wyoming over the last decade.

"It's very, very rare" for lions to attack, said Wyoming Game and Fish spokesman Warren Mischke. "We're still trying to investigate why this lion would behave this way."

The wounded animal retreated after Britton inflicted a six- to eight-inch gash on the lion's shoulder, leaving him with only a small puncture wound on his forearm.

"You would think if you hit an animal with a chain saw it would dig right in," he said. "I might as well have hit it with a hockey stick."

The mountain lion was shot and killed Monday after it attacked a dog brought in to track the animal, which was 4 to 5 years old. Authorities say it was in poor physical condition and appeared to be starving.

After Britton's confrontation, he and his wife, Kirsta, decided to spend the night in their pop-up camper with their two children rather than risk packing up with the lion still on the loose.

Wildlife agents were called the next morning after Britton told a passing U.S. Forest Service employee about the incident.

Tests for rabies and other diseases came up negative, but officials said they were continuing to analyze the animal for other potential diseases.