Fire officials said a man who lives in a commercial space in an office building at 318 Squire Road was watching the dog for a friend when he invited another friend over.
Authorities said when the men fell asleep, the dog randomly attacked the guest, before running out a back door of the building.
The men called 911 and police were able to locate the dog nearby. Animal control was called in to safely remove the dog.
Fire officials said the man who was attacked was taken to Mass General Hospital to be treated for extensive arm injuries.
Police are investigating whether charges will stem from the dog attack. A secondary investigation is underway to determine whether the man living in the office building will face charges for code violations.
Meanwhile, Paul Byron says the sleeping man must have "provoked" the pit bull into attacking him...