Redirect to 404 Page

functions.php

global $wp_query;
$wp_query->set_404();
status_header( 404 );
get_template_part( 404 );
exit();

/**
 * Show 404 No Found Page on Single View of Custom Post.
 */
function wpse_128636_redirect_post() {
	$queried_post_type = get_query_var( 'post_type' );
	if ( is_single() && 'career' == $queried_post_type ) {
		global $wp_query;
		$wp_query->set_404();
		status_header( 404 );
		get_template_part( 404 );
		exit();
	}
}

add_action( 'template_redirect', 'wpse_128636_redirect_post' );