SEATTLE — The two mountain bikers did what they were supposed to do when they noticed a mountain lion tailing them on a trail east of Seattle.

They got off their bikes. They faced the beast, shouted and tried to spook it. After it charged, one even smacked the cougar with his bike, and it ran off.

It wasn’t enough, authorities said.

As they stood trying to catch their breath, the cougar returned, biting one of them on the head and shaking him, Capt. Alan Myers of the Washington Department of Fish and Wildlife Police said Sunday.

The second cyclist ran, and the animal dropped the first victim and pounced on him, killing him and dragging him back to what appeared to be its den.

“They did everything they were supposed to do,” King County sheriff’s Sgt. Ryan Abbott said. “But something was wrong with this cougar.”

The attack Saturday near North Bend, in the Cascade Mountain foothills 30 miles east of Seattle, was the first fatal cougar attack in the state in 94 years. Myers said Sunday that the cougar was underweight — about 100 pounds when a typical 3-year-old male in the area would be 140 to 180 pounds.

The 31-year-old Seattle man who was bitten first, Isaac Sederbaum, survived. Rescuers flew him to a hospital, where he was in satisfactory condition Sunday.

Myers identified the deceased victim, a 32-year-old Seattle resident, as S.J. Brooks.

After the cougar attacked Brooks, a badly bloodied Sederbaum managed to get on his bike and ride off. He rode for 2 miles before he could get a cell phone signal to call 911.

When rescuers arrived, it took about half an hour to find Brooks, who was dead with the cougar on top of him in what appeared to be a den-like area. An officer shot at it, and it ran off. Several hours later, Washington Department of Fish and Wildlife agents used dogs to track it to a nearby tree. They shot and killed it.

Authorities plan to match DNA taken from the animal with DNA from the victims to be certain they killed the right cougar. They sent the animal’s carcass to a veterinary lab at Washington State University for a necropsy to determine what might have been wrong with it.