The Massachusetts Department of Correction is responsible for operating the prison system of the Commonwealth of Massachusetts, US  The Massachusetts Department of Correction is responsible for the custody of about 10,000 inmates (as of January 2016) throughout 17 correctional facilities and employs over 5,200 employees (about 4,000 of whom are sworn correctional officers). The Massachusetts Department of Correction also has a fugitive apprehension unit, a gang intelligence unit, a K9 Unit, a Special Reaction Team (SRT), and a Tactical Response Team (TRT). Both of these tactical units are highly trained and are paramilitary in nature. The Massachusetts DOC is the largest law enforcement agency in the state of Massachusetts with a staff of 5,200, about 4,000 of whom are sworn correction officers. The agency is headquartered in Milford, Massachusetts and currently headed by Commissioner Carol Higgins O'Brien.