More than a dozen angry members of the Mahopac Volunteer Fire Department showed up to a White Plains courtroom on Wednesday to watch their former treasurer get sentenced to over six years in prison for stealing $5.7 million from the department’s coffers. Federal Judge Cathy Seibel called Michael Klein’s thefts — pulled off in 275 transactions over 13 years — “mind-blowing” before sentencing him to 77 months in prison. Seibel also ordered Klein to pay restitution of $5.5 million, including $4.5 million to the all-volunteer fire department, which has had its budget slashed as a result of Klein’s thefts.