Officer Scott Knablin was the focus of an internal investigation following the death of Julie Minogue last December.

Minogue's ex, Ewen Dewitt, is accused of killing her with an ax. She had previously filed a complaint against Dewitt.

Police say Dewitt had a history of violence with Minogue, who had a protective order against him. Minogue filed a complaint against Dewitt for sending her over 200 text messages in violation of the order.

Dewitt wasn't taken into custody because Knablin never resubmitted an arrest warrant application with additional information, according to police.

News 12 was told Knablin submitted a letter of resignation in July.

Minogue's family is planning to sue the city and police department. A formal notice says her death was "preventable."

Her body was found on Dec. 6 in a pool of blood with an ax nearby, authorities say. Police had said Minogue's son found his mother on the floor and Dewitt nearby holding the ax.