The attack came suddenly during the pair’s regular walk through their favorite place in Montana

When a grizzly bear threw Kate Cholewa, 53, to the ground and jumped on her, his teeth ripping into her head, Cholewa’s black lab mix leapt into action and saved her life.

The attack came suddenly during the pair’s regular walk through their favorite place, Point of Rocks Fishing Access Site, not far from their home in Emigrant, Montana, near Yellowstone National Park.

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“We were walking along enjoying ourselves,” Cholewa recounted to PEOPLE.

The Chicago native, who moved to Montana to attend graduate school in 1987, had never encountered a bear or even seen tracks during her walks with Carmen the dog, who she adopted as a pup 12 years ago and now weighs about 90 pounds. Like all area residents, though, Cholewa is well aware that bears are prevalent. The best way to avoid bear encounters, as signs throughout the area warn, is to ensure the animal hears your approach.

So it wasn’t unusual that Cholewa sang as the two walked during the early afternoon of Monday, Oct. 12. She was actually midway through a rendition of Dido’s part in the Eminem song “Stan” when she glanced over and saw the hair on Carmen’s back standing up in a way she’d never seen before.

Until recently Carmen had always led the way on their walks. But after she was diagnosed with a torn ACL a year ago, Cholewa started taking the lead to protect Carmen’s delicate rear left leg. Though surgery could repair the tear — which vets predicted would result in Carmen’s death within six months of diagnosis — Cholewa sought alternate treatment so Carmen wouldn’t be traumatized by months of confinement in a kennel. Carmen continues to thrive.

“I was about two steps ahead of her when I turned and was face-to-face with a bear,” says Cholewa, who estimates the bear weighed about 500 pounds. “I have no idea if it jumped on me or hit me. All I know was that I was suddenly on the ground with a bear on top of me. I remember thinking ‘I’m going to die.’ “

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Cholewa couldn’t see past the bear but felt Carmen’s presence and thought she heard her barking. Suddenly the bear stood up.

“I knew I was supposed to play dead, but I just couldn’t stop from scrambling away,” she says. “All I could think was that my dog was still there, probably being ripped apart.”

And that thought tore her heart apart.

Cholewa adopted Carmen from the Missoula Humane Society when the canine was just a puppy, and it didn’t take long for the duo to bond.

“I wanted a dog that loved hanging out, was content to just be with me while I worked,” says the author of the novel of Shaking Out the Dead, who is midway through her next book. “We bonded right away.”

Of course there’s no way that Cholewa could have known the extent to which that bond would be tested.

As she scurried from the attack, her heart pounding with fear, she grabbed her cell phone and called 911. As the operator asked if the bear followed her, Cholewa heard a rustle and turned to see Carmen bolt to her side.

“The only time I let go of my head [that was gushing blood] was when I was helping Carmen into the car,” she says. “Usually I help her because of her leg, but we both jumped in the car and waited” for the police to arrive.

As the ambulance transported Cholewa to the hospital, she told rescuers of her concern about Carmen. They assured her that Carmen was at Stafford Humane Shelter in Livingston, where she was cared for until Cholewa brought her home.

“It meant so much to know she was cared for and not alone,” says Cholewa. “I think it’s wonderful there are such places where I could adopt her and then would care for her when I couldn’t.”

Cholewa and Carmen are working to return to everyday life, though Cholewa doubts they ever truly will. That’s not because of the scrapes, cuts and bumps on Carmen or Cholewa’s facial bruises and head lacerations.