A rare and extremely gruesome cougar attack took place over this weekend, which ended with one biker dead and the other with serious injuries in a hospital. The cougar was relentless in catching its prey and the two bikers happened to be that prey for the very emaciated animal. The cougar killed one of the bikers and dragged his lifeless body back to its den.

Two veteran bikers were cycling down the wooded trails of the Cascade Mountain foothills in Washington State when they noticed they were being followed by a cougar. Both men got off their bikes and made noise to scare the cougar away, which is protocol when coming across one of these wild animals, according to Fox News.

Clamping on to biker's head with its jaws

The cougar left but returned with a vengeance, attacking the men and overpowering the two with its force. The cougar grabbed Sonja "SJ" Brooks, violently shaking him while he had his entire head inside his jaws. When the second biker, Isaac "Izzy" Sederbaum, attempted to get away, the cougar spotted him, making a dash for it -- dropping his friend to dart after him.

Sederbaum attempted to fight the cougar off using his bicycle as a weapon and the cougar finally retreated but not before seriously injuring him. He made his getaway as the cougar went back to the body of his friend, carting him off into the woods.

No cell service

Sederbaum was able to make it to an area about two miles away from the site of the attack where there was cell phone service.

He called 911 and waited for help to arrive.

Drags body off to its den and stands guard

When authorities arrived they found the very emaciated cougar standing on top of Brooks' body near its den.

The animal was euthanized and the remains were sent to the lab to determine if the cougar was sick. This is the first time in almost a century that a cougar attack ended in the fatality of a human.

King County sheriff's Sgt. Ryan Abbott said that the two men did everything they were supposed to do when encountering a cougar in the wild.

But something else seems to be at play here with the animal itself. Officials believe something was wrong with the cougar.

Something very wrong with animal

A brain necropsy will be done to determine just what was wrong with the animal. The cougar was thought to be about 3-years-old and at that age it should weigh somewhere between 140 to 180 pounds. This cougar weighed about 100 pounds and was severely underweight, according to Washington Department of Fish and Wildlife Police Captain Alan Myers.

The officials did not speculate on what type of sickness would cause this cougar to attack. Although it was clear to them that something was wrong with the animal just by looking at it, and by the behavior it demonstrated with this attack.