Three people were hospitalized, two with serious injuries, after being attacked by a dog Friday afternoon in Chester.

The victims’ identities were not available at press time. One of the victims was the owner of the dog, according to the Plumas County Sheriff’s Office.

A deputy responded to a call for “a dog bite” about 4 p.m. Sgt. Ian James arrived at the scene and found three people with injuries.

The dog, a 140-pound French mastiff, was contained in the backyard of the residence.

Several emergency responders arrived on the scene to provide aid and transportation to the injured people.

The dog’s owner reportedly suffered the most serious injuries. He was flown to Enloe Hospital in Chico with severe arm and head wounds. His condition was unknown.

Two victims were transported to Seneca Hospital in Chester. One female had a “major bite” on her leg. The third victim was treated and released.

According to James’ report, the dog was tranquilized and taken to the Plumas County Animal Shelter, where it died.

Assistant Sheriff Dean Canalia said the mastiff likely died from a heavy dose of medication.

“We weren’t going to take any chance of having our animal control officer injured,” Canalia said. “It was a very big dog.”

The sheriff’s office said the dog was being tested for possible disease.

James offered the department’s thanks for the emergency personnel who responded, including Chester fire, Peninsula fire, Lake Almanor West fire, Enloe Flight Care and the California Highway Patrol.

It was unknown how or why the dog attacked.