An otherwise normal, mid-morning mountain bike ride turned deadly when a cougar attacked two cyclists near Seattle on Saturday.

One of them, 31-year-old Isaac Sederbaum, survived—but only after wrestling his head free from the cat’s mouth. The other cyclist, 32-year-old S.J. Brooks, wasn’t so lucky; after turning away from Sederbaum, the cat pounced on, killed, and dragged Brooks into the woods.

Sederbaum, seriously injured and seeing that there was nothing he could do for his friend, rode two miles to an area with cell service and called for help. When authorities arrived, they found the cat atop Brooks’s body, which had been partially covered with debris. After cornering the cougar up a nearby tree, agents from the state’s Department of Fish and Wildlife euthanized the animal.

Though sad and sickening, these sorts of attacks are exceptionally rare; in Washington, this is only the second recorded puma-related fatality in the last 94 years. Today, officials are necropsying the cat to try and determine what may have provoked such unusual behavior from a species that biologist Mark Elbroch describes as “timid” and reluctant to engage.

“What this mountain lion did to these people is totally abnormal,” says Elbroch, lead puma program scientist for Panthera, the global wild cat conservation organization. “This was an animal that was not healthy, and in its last attempts to try to survive did something it ordinarily wouldn’t.”

Consummate Predators

Pumas, which are also called cougars, mountain lions, and about a dozen other names, are stalk and ambush predators—meaning they prefer to sneak up on and surprise prey, rather than engage in prolonged fights or chases. Once they pounce, the cats typically bite through the base of their prey’s skull, where it connects to the neck, then they drag the carcass to a secluded spot and cover it, sometimes returning to the kill and feeding from it for days.

Pumas once roamed nearly the entirety of the Americas, with an ancestral range that extended from the Canadian north to the southern tip of South America. Now, though, humans have reduced that range to a fraction of the original. With the exception of a remnant population in Florida, the cats are rarely seen east of the Mississippi—though it does occasionally happen—and in January the Eastern cougar population was officially declared extinct. But in some areas in the West, puma populations are rebounding and doing quite well, including the area in Washington where Saturday’s attack occurred.

Normally, though, you’ll never see a puma or even know they’re around. The cats are supremely secretive, taking great care to slink through underbrush and avoid activity during the day. With a predilection for hunting at dusk and dawn and an uncanny ability to leap high into trees, pumas are the ninjas of the feline world.

“The mountain lion you do not see is the one that’s hunting,” Elbroch says. “One that walks up aggressively is not hunting.”

Pumas and People

Normally, pumas will do their best to avoid us. But every now and then, something goes wrong. Since the early 1900s, there have been about 120 or so documented attacks on humans, according to the Washington Department of Fish and Wildlife. Of these, 25 have been fatal for the humans. The story is different for the cats, many of which have been killed during the attack or afterward.

“It is necessary to remove a mountain lion that is not just threatening, but attacking people in a human-dominated landscape,” Elbroch says. “That is not a judgment, that is a fact. We cannot allow a mountain lion to attack people and then to go free.”

But the fact that roughly 120 attacks on humans have been documented over more than a century suggests the rarity of the occurrence, given that millions of people live among hundreds of thousands of cats.

In most situations, the best way to deflect a cougar attack is to make yourself appear as large as possible, shout, slowly back away, and throw whatever is within reach. A recent study shows that if you run, the odds that you will be attacked increase—and the odds that it will be a fatal attack also go up (scientists suspect this is because running triggers the puma’s natural predatory response).

Most importantly, if the cat still decides to attack, fight back.

“Most of the attacks over the last chunk of years in which people have attempted to defend themselves, they have successfully done so—they’ve scared off or even killed the puma,” Elbroch says.

Encounters on the Rise

Why this didn’t work for Sederbaum and Brooks, who apparently swung a bicycle at the cat, is still a mystery, but Elbroch and others suspect it’s because the cat was in very, very bad shape. A young male, the puma weighed about 100 pounds and was quite emaciated, possibly the result of disease, injury, poisoning, or who knows what.

“Those animals that are unhealthy or hindered in some way, whether they have an injury or are starving, they are more likely to exhibit these sorts of dangerous behaviors,” Elbroch says. “They’re going to engage prey they wouldn’t normally engage, they’re going to be active at times of day they wouldn’t normally be active, they are going to encroach in areas where they wouldn’t necessarily feel safe.”

In other words, just like some humans are known to do crazy, violent and risky things, the same can be true for cats.

Encounters between humans and cats are on the rise. But this isn’t surprising, for at least two reasons: Puma populations are rebounding from the bounty-hunting of the last century, which dramatically reduced the cats’ numbers throughout the West. And, growing human populations are moving farther and farther into the cats’ territories, which are being sliced up by roads, ranches, and other obstacles.

“There’s no sign that mountain lions are any more aggressive than they ever have been,” Elbroch says, noting that peacefully coexisting with our carnivorous neighbors takes a certain amount of responsibility, especially in areas where livestock make tempting targets.

“We can’t just expect the cats to know the rules that we have created and they should follow, and expect that they will know there will be consequences if they don’t follow them,” he says. “That really applies more to livestock predation and not human safety.”