A pregnant Florida woman stabbed and killed her family's dog Friday after the pit bull attacked the woman's mother and sister.

According to a Pinellas County Sheriff's Office news release, the male dog named Buster got loose in the family's Safety Harbor home and fought with another male pit bull around 4 p.m. Friday. Heidi Cooper, 45, and her 14-year-old daughter tried to pull the dogs apart, but Buster turned and attacked them, the PCSO said.

That's when 22-year-old Sierra Willson stepped in, stabbing Buster several times with a knife, according to the news release. Willson is eight months pregnant, according to the Tampa Bay Times.

When first responders arrived, Buster was dead in the family’s front yard.

Cooper sustained serious injuries in the attack, including puncture wounds and lacerations, the sheriff’s office said. Her younger daughter also was wounded, but not as seriously. All three were taken to Bayfront Health in St. Petersburg for treatment.

According to the sheriff’s office, Buster was “normally kept in a separate room because he was known for being aggressive.”

In an interview with The Tampa Bay Times, Willson called Buster “an amazing dog” and said he will be missed. On her Facebook page, Willson posted a photo she said was taken with Buster “20 minutes before he turned. Completely unprovoked,” she wrote. “No reasoning behind it at all.”

She also wrote that she had received threats after the incident, and added that she does not regret what she did. “It was either him or my mom,” she wrote. “Nobody knows what they would do in that situation.”