IOWA CITY, Iowa (AP) – An Iowa State Patrol supervisor fired for misconduct is blaming his actions on an addiction to powerful painkillers. Sgt. Michael Haugen wrote in a letter released late Monday that he became addicted to opioids after battling medical conditions in recent years. He says his addiction “negatively impacted my family, friends, co-workers and others” and that he’s taking responsibility.

The Iowa Department of Public Safety moved to fire Haugen last month for misconduct that it has refused to explain. Haugen declined to appeal his termination by Monday’s deadline, instead submitting the letter resigning his position with the patrol in Mason City. He says he needs to “focus on my health and family.”

Haugen rear-ended another car in March in his state vehicle, but the patrol’s investigation blamed the front driver.