Officer 's attorney , union representative submit ##ant 's letter of resignation . Police : Office investigating ` ` mental state '' of officer involved in shooting . Officer says Johannes Mehserle has been shot twice because of . Video shows officer shoot him in back as another officer kneels on him .
Officer 's attorney , union representative submit officer 's letter of resignation . Prosecutor : Office investigating `` mental state '' of officer accused in killing . Spokesman says Johannes Mehserle has been moved twice because of . Video shows officer shoot Grant in back as another officer kneels on him .