Dr. Richard Polsky posits that Bethany Stephens either "did something to one of the dogs or one of the dogs experienced something to trigger its aggression towards her"

A well-known dog expert tells PEOPLE its unlikely we will ever know what triggered last week’s attack on Virginia woman Bethany Lynn Stephens, who was mauled to death by her two pit bulls while on a walk with them in the woods. But the expert has some theories on what might have happened.

Dr. Richard Polsky, an academically trained expert on animal behavior and dog bites, says it is unlikely recent changes in their lives contributed to the canines’ homicidal aggression last Thursday — despite what authorities have said.

On Monday, authorities told reporters the animals had been “neglected” recently after being left Stephens’ father, who “was not taking care of the dogs.” The two animals, they said, had become “more isolated” with “less and less human contact” leading up to the attack.

“If kept isolated more and more over time, I would imagine these dogs would have been happy to see their owner,” explains Polsky, who has more than 25 years of professional experience. “If you were keeping them isolated, I could see that playing into an attack on a stranger, especially if the dogs felt their safety was being threatened.”

Bethany Lynn Stephens
| Credit: Facebook

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Stephens, 22, of Glen Allen, was found Thursday evening in the woods near an old family farm where she frequently walked her dogs, after her father called 911 around 8:20 p.m. to report that she hadn’t returned home.

By all accounts, Stephens had a loving relationship with the dogs, who were euthanized not long after being found after the attack. Given that, Polsky believes that something in their immediate environment must have triggered one or both of the animals.

“There had to have been something out there in the environment that triggered this and we don’t know what it was,” Polsky explains before listing several common triggers: the doorbell ringing, a territorial invasion, and violence. “Usually with these attacks, one dog starts it and the other one joins in, which is what I suspect happened here.”

Polsky posits Stephens either “did something to one of the dogs or one of the dogs experienced something to trigger its aggression towards her.”

He speculates she may have “corrected the dog in some way, or dog may have chased after a squirrel or encountered a dead animal; the dog was very interested in investigating it, she pulled the dog away which frustrated the animal, and he redirected his aggression towards the owner.”

Over the last two decades, he says there have been between 30 and 45 fatal dog attacks in the United States. Polsky admits that most involved pit bull-type dogs but notes Rottweilers and mastiffs have also attacked humans. Almost always, the dog is male with little to no socialization or training, he says.

“Most of the victims are very young or old, and they have no defense against a big, strong muscular dog,” Polsky tells PEOPLE. Like in Stephens’ case, “most of these incidences happen when the victim is alone.”

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He believes investigators will delve deeper into Stephens’ relationship with the dogs she raised from the time they were puppies.

“They need to look into how often she walked these dogs in this area, if the dogs ever showed any aggression towards her, if she had history of punishing the dogs…there are just so many unanswered questions here,” Polsky says. “Most owners, they love their dogs, so they ignore signs of a dog’s potential danger, thinking they’ll outgrow it. It could have been something minor that made the dog turn on its owner.”