wp_delete_attachment doesn't delete images in wp-content/uploads/

My function lets users delete their uploaded images in the front-end. However, they're only deleted in the Media Library. That means that they're still in wp-content/uploads/.

     public static function removePhoto($ID, $attachment) {
     if(isset(self::$data['user']['photos'][$attachment])) {
    unset(self::$data['user']['photos'][$attachment]);
        wp_delete_attachment($attachment);
        core:updateUserMeta($ID, 'photos', self::$data['user']['photos']);
    }
}

Any ideas?