A Renton police officer accused of slapping and groping a confidential informant last month has resigned, according to the police department.

The department announced Tanuj Soni’s resignation in a statement Thursday. Soni, who had been a Renton police officer for eight years, was charged with fourth-degree assault with sexual motivation and abuse of office in King County Superior Court last month.

Prosecutors say Soni asked a confidential informant to meet him in a Des Moines park early in the morning of Aug. 10, telling her he needed to discuss something important related to a case they’d been working on. According to charging documents, the woman said Soni told her to drink and take off her clothes, then slapped her face and buttocks and grabbed her genitals. She told police she was too afraid to resist but eventually managed to run to a nearby home for help, according to charges.

The Renton Police Department placed Soni on administrative leave after his arrest and launched its own investigation, which found several policies had been violated, according to the statement. Soni resigned as the department was preparing to fire him, said police spokesman Cmdr. David Leibman.

Soni is scheduled to next appear in court on Oct. 15.