A man was horrified to arrive home Monday and find that his wife had been killed by the family dog, which had been adopted just a week before.

Dawn Brown, 44, a volunteer firefighter in Illinois, was found dead in her Big Rock home. She had suffered bites to her neck, according to the Chicago Tribune.

Her husband Bob, also a firefighter, discovered her at 4:15 p.m., hours after the family's 140-pound mastiff attacked her. He called 911, and fellow firefighters responded.

"We had some really emotional firemen that were there on the scene first," Bristol Fire Department Lt. Pat Gengler told FOX 32. "To get to the process of talking to people and interviewing everybody including the husband took some time."

Police are still trying to determine why the dog mauled her, but police say that the family's pit bull mix and boxer were not involved.

The Browns had taken in the mastiff a week earlier from a family member who didn't want it anymore, the Daily Mail reports. It's yet unclear whether the dog had any past violent behavior, but the previous owners maintained that they had not given it away because it was aggressive.

The couple began training with the Big Rock Fire Protection District in 2003.