show posts by category with short code

<?php 
function site_news_posts(){
    $query_args = array(
        'category_name' => 'category_name',//chooose category
        'posts_per_page' => 4,//number of posts to show
    );
    $query = new WP_Query($query_args);
    if ($query->have_posts()) {
        echo '<div class="row">';
        while ($query->have_posts()) {
            $query->the_post();
            echo '<div class="col-md-3">';
            echo '<a href="' . get_permalink() . '">';
            the_post_thumbnail('post-thumbnail', '');
            echo '<h4 class="pu-news-title">' . get_the_title() . '</h4></a>';
            the_excerpt();
            echo '<div class="pu-news-meta">';
            echo '<span>Posted on: ' . get_the_date() . ' | </span><br><span>';
            comments_number();
            echo '</span></div>';
            echo '</div>';
        }
        echo '</div>';
        /* Restore original Post Data */
        wp_reset_postdata();
    } else {
        // no posts found
    }

}
      //create the shortcode
        add_shortcode( 'news_posts', 'site_news_posts' );
        // echo the_short code
       echo do_shortcode("[news_posts]");