SAFETY HARBOR — A pregnant 22-year-old had to stab her family dog to death after it "turned" on his owners Friday, according to the Pinellas County Sheriff's Office.

Sierra Willson stabbed the dog after it began viciously attacking two other dogs and then its owners, including Willson's mother, Heidi Cooper, 45, and her sister, Meaghan Tokay, 14.

Buster, a pit bull, was known to be aggressive and kept away from two other dogs in the home at 765 West Gate Drive in Safety Harbor, said Sheriff's Office spokesman Spencer Gross.

"At some point, Buster got out and started attacking the other two pit bulls," Gross said. "The mother and two daughters tried to intervene but Buster turned on them and bit them numerous times."

The family was treated at Bayfront Health St. Petersburg for the bites and other non-life-threatening injuries, Gross said.

Reached via Facebook, Willson declined to speak with a reporter Friday evening.

On her page, she wrote that she was due to deliver a son in just seven weeks. She also regularly wrote about her dogs: a female and two males, pure-bred pit bulls.

She stayed home during Hurricane Irma to be with them. She posted a photo of Buster in September with a blue heart next to his name.