How make HTTP status 404 for certain page – Magento 2

I try to make some pages with 404 status and ouptut 404 page but with current url.
I do it in observer.
This is my events.xml

<event name="catalog_category_load_after">
    <observer name="empty_to_404" instance="ProviderModuleObserverCatalogEmptyTo404" shared="false"/>
</event>

This is a class of Observer

    /** @var ResponseFactory */
    protected $responseFactory;

    /** @var UrlInterface */
    protected $url;

    protected $registry;

    public function __construct(
        ResponseFactory $responseFactory,
        UrlInterface $url,
        Registry $registry,
        Http $http
    ) {
        $this->http = $http;
        $this->responseFactory = $responseFactory;
        $this->url = $url;
        $this->registry = $registry;
    }
    /**
     * @param Observer $observer
     * @return void
     */
    public function execute(Observer $observer)
    {

        /** @var MagentoCatalogModelCategory */
        $category = $observer->getData('category');
        $fullActionName = $this->http->getFullActionName();
        $productsCount = $category->getProductCount();

        if ($fullActionName == 'catalog_category_view' && !$productsCount) {
            // Do page 404 status

            $redirectionUrl = $this->url->getUrl('cms/noroute');

            /** @var ResponseHttp $response */
            $response = $this->responseFactory->create();
            $response->setRedirect($redirectionUrl, 404)->sendResponse();

            return $this;
        }
    }

I’v got a redirect to 404 page and to 404 url.

What is the right way to do it? Also, what event name will be prefer?