Definition of inside job in English English dictionary
A crime or other illicit action committed by or with the help of someone either employed by the victim or entrusted with access to the victim's affairs and premises
It seems to me it must have been what the police at home call an inside job; because whoever it was apparently knew the combination of the safe.
some transgression committed with the assistance of someone trusted by the victim; "the police decided that the crime was an inside job
A crime perpetrated by, or with the help of, a person working for or trusted by the victim
crime against a business or organization committed by an insider or with the help of an insider