A husband has returned home to find his firefighter wife killed by a dog they adopted from a family member just a week ago, police said.

Dawn Brown's husband discovered her body in their home in Big Rock, Illinois at 4.15pm on Monday, after she had suffered bites to the neck, Kane County Sheriff’s police Lt. Pat Gengler said.

Investigators determined the fatal wounds had been inflicted hours earlier that morning by a mastiff inside the home shared by the couple, who also have a boxer and a pit bull mix.

Dawn, 44, and her husband Bob had taken in the mastiff just a week ago from a family member who did not want it anymore,

The couple, who are childless, regarded their two older dogs as their children,