CHEYENNE, Wyo. (AP) — Campbell County Sheriff Bill Pownall is resigning from office in the midst of a state investigation into an allegation that he tried to suppress his son's arrest on a drunken driving charge.

Pownall wrote to Campbell County commissioners on Wednesday announcing he's resigning effective Dec. 1.

Gov. Matt Mead earlier this month announced he has directed the Wyoming attorney general's office to undertake removal proceedings against Pownall.

Mead made the announcement after reviewing a report from the Wyoming Division of Criminal Investigation. The agency investigated an allegation that Pownall pressured deputies to drop a drunken driving charge against his 23-year-old son, Seth Pownall, in August and change it to a charge of being a pedestrian under the influence. County prosecutors have refiled the DUI charge.