BUTLER TWP — Township commissioners approved the retirement of police sergeant Timothy Clark on Monday night, bringing the total number of departures from the township’s department to five officers since mid-2016.

“This is kind of unusual,” said Dave Zarnick, the president of the township board of commissioners. “We’re surprised we had this big of a turnover in our police department. But the timing was right.”

Clark is the second sergeant to retire from the department and the fifth officer overall. Two of the retiring officers took positions with the Butler County Sheriff’s Office, one took a job with Pennsylvania State Police, and two officers left law enforcement entirely.

Zarnick said the departures had nothing to do with the township shifting its police schedule early last year to 12-hour shifts. Commissioners spoke with the retiring officers and were told scheduling wasn’t an issue for them, he said.

Clark’s last day will be Jan. 26, according to board members, though he will be on the department’s payroll until April 11, giving him 27 full years of service with the township’s department.

Police Chief John Hays said the department has filled the open positions left by retiring officers as they’ve left, but Clark’s retirement will leave another sergeant post vacant. The department has 21 positions in total, but only three of four sergeant positions are filled currently, because of an earlier retirement. When Clark leaves duty on Jan. 26, that will mean the department has only two sergeants on its staff. In the department’s administrative structure sergeants oversee rotating shifts of officers as they come on duty each day. Hays said the shifts that have no sergeant will be overseen by a senior officer in charge — usually determined through seniority — until the township can schedule exams and complete promotions to fill the positions.

There was no immediate indication on Monday of how long that might take. Hays said the township follows the state’s civil service rules and regulations when it comes to promotions within the police department. Candidates for sergeant must have at least five years of experience and no letters of reprimand in their personnel file.