The two mountain bikers, authorities say, did what they were supposed to do. They made loud noises to drive the cougar away. One of them even struck the animal with his bicycle.

But none of it worked. The big cat that had been following the two friends as they were mountain biking in rural Washington state pounced, lunging at one of the cyclists' head and killing the other, whom the animal mauled in its den.

The attacks Saturday morning - the first fatal one in the state in nearly a century - was uncharacteristic of cougars, which are normally solitary and easy to scare away.

Authorities hope that a brain necropsy would reveal whether "something else was going on," Sgt. Ryan Abbott, spokesman for the King County Sheriff's Office, told The Washington Post on Sunday.

"Something was wrong with this cougar," Abbott told the Associated Press.

On Sunday, Capt. Alan Myers of the Washington Department of Fish and Wildlife said the 100 pound (45 kilogram), 3-year-old male cat was "emaciated," the Seattle Times reported. Adult male cougars usually weigh 140 to 180 pounds (64 to 81 kilograms).

Myers on Sunday also identified the victims: 32-year-old S.J. Brooks and 31-year-old Isaac Sederbaum, both of Seattle, according to the Seattle Times.

The two were mountain biking on a dirt road near North Bend, a foothills town 30 miles from Seattle, about 11am, when they realized that a cougar was chasing them.

They managed to drive the cat away, at least at first, by making loud noises - something that authorities recommend people do during such encounters. The cougar ran toward the bushes after one of the victims swung his bicycle, Abbott said.

But just as the two were about to leave, the cougar jumped back and pounced on Sederbaum, holding his head with its jaw and shaking him from side to side.

At one point, Brooks got off the bike and ran away, catching the attention of the big cat, whose instinct was to chase.

Injured and bloodied, Sederbaum hopped on his bike and rode away. He looked back and saw the cougar dragging his friend into the woods, Abbott said.

Sederbaum rode about two miles to find cell reception and called 911. He suffered deep cuts throughout his body and was taken to Harborview Medical Center in Seattle, where his condition was later upgraded to satisfactory, according to media reports.

First responders from the fire and sheriff's departments found Brooks in the cougar's den, Abbott said. One of the deputies fired a shot, scaring the animal away.

Myers told the Seattle Times that Brooks was severely mauled.

Officers with the Washington Department of Fish and Wildlife used hounds to track the cougar, which they found behind a tree 80 feet (24 metres) away, Abbott said.

The animal was later euthanized. The carcass was taken Sunday to Washington State University in Pullman, where a veterinarian will examine the animal's brain, the Seattle Times reported.

Friends said Brooks was an avid cyclist who moved from Boston to Seattle not long ago and immediately fell in love with the outdoors. Tyler Gillies said Brooks had been leading cycling trips in the past year to the remote area where the attack occurred.

"I have so many friends that ride out there all the time," Gillies told KIRO.

"I do the same thing myself. It is a perfectly safe and wonderful thing to do. And S.J. was in the wrong place at the wrong time, and I'm just crushed."

Abbott said the area is known for cougar sightings, but attacks are extremely rare.

Before Saturday, 16 cougar attacks, one of which was fatal, had been reported in Washington state during the past century. The first known fatal attack occurred in the 1920s, when a boy named Jimmy Fehlhaber was devoured by a male cougar.

About 120 attacks, 25 of which were fatal, have been reported in the United States and Canada in the past 100 years.

However, attacks involving cougars, also known as mountain lions, have been increasingly common in the past 20 years as humans encroach on wildlife habitats.

In Washington state, for example, seven of all reported attacks occurred during the 1990s.

According to the Washington Department of Fish and Wildlife, 1-to-2-year-old cougars that have become independent of their mothers are more likely to attack domestic animals and humans.

"When these young animals, particularly males, leave home to search for territory of their own, and encounter territory already occupied by an older male cougar, the older will drive off the younger one, killing it if it resists. Some young cougars are driven across miles of countryside in search of unoccupied territory," the agency said.

If you encounter a cougar, don't run - because the animal's instinct is to chase. Instead, authorities advise people to never take their eyes off the animal and to try to appear larger and more intimidating. Shout, wave your arms and throw rocks, anything to let the animal know you are a threat and not prey.

"If the cougar attacks, fight back aggressively and try to stay on your feet," according to the Washington Department of Fish and Wildlife. "Cougars have been driven away by people who fought back."

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This article was originally published by The Washington Post.