CASPER, Wyo. (AP) — A longtime Wyoming prosecutor says he will step down at the end of his term in December.

The Casper Star-Tribune reports Natrona County District Attorney Michael Blonigen announced his retirement Tuesday, citing plans to practice law privately.

Blonigen says he wants to "get back to a more hands-on law practice," something that has fewer administrative duties.

Blonigen became district attorney in 2004 and has worked in the prosecutor's office for more than 30 years. He has prosecuted several high-profile murder cases, leading to convictions in multiple cold cases.

Blonigen says his retirement has been an open secret as he had made the decision years earlier.

Assistant District Attorney Dan Itzen is running for the top prosecutor job. He's currently the only declared candidate for the office.