def parse_user_delete_sync_agent_data(json):
    """
    Parse the incoming statement for a sync agent event concerning a user deletion.

    :param json: A statement concerning a user deletion.
    :type json: dict(str, NoneType)
    :return: A dictionary containing the user id of the deleted user.
    :rtype: dict(str, str)
    """
    statement = json['statement']
    user_id = statement['object']['id'].split("=")[-1]
    sync_user_delete_data = {
        'user_id': user_id,
    }
    return sync_user_delete_data