Meridian Police Chief James Reed announced his resignation Monday.
Reed made a brief statement saying he's stepping down for personal reasons. Then he left the room.
The fact that Reed is not a certified law enforcement officer in Mississippi came to light last week.
Mayor Cheri Barry also spoke briefly, but neither accepted questions at the news conference that was called by the mayor.
Barry later issued a written statement in which she thanked Reed for his service to Meridian.
"James Reed is a hometown hero for Meridian. He has served with distinction in law enforcement for more than thirty five years as an investigator with Mississippi Department of Justice, a probation and parole officer with the State of Mississippi, and as a supervisory special agent with the Naval Criminal Investigative Service," said Barry. "My decision to accept his resignation came only after deep thought and prayer."
Barry selected Assistant Chief James Sharpe to serve as acting chief of police.