Department veteran, William Tierney, will take over as chief on Monday. The Board of Commissioners made the appointment official Wednesday night. Tierney has been with the Hatfield Township Police Department since 1985. Tierney started as a patrolman, then moved up to Sergeant in 1998 and Lt. in 2007. Tierney takes over for retiring Chief Mark Toomey who was appointed Chief in 2003. Toomey joined the department in 1977.