Automatic category assignment upon attachment upload

Lets say the media library has the following category [news, events, photo, page, post]

Your wordpress also has the above 5 set as post-type. What I want is when

1- Events -> Add New

2- File is uploaded while adding a new events post-type

3- File Finished uploading, wordpress should automatically attach events category for that attachment file.

I have code to update the category to a set value after upload, but could not find the currently editing post-type when running this function.

adds category 3 to the uploaded file

 function add_category_automatically($post_ID) {
            wp_set_object_terms($post_ID, array(3) or 'cat_slug_goes_here', 'category', true);
    }
    add_action('add_attachment', 'add_category_automatically');

gets currently editing post-type via ID (this displays correctly)

add_action( 'admin_init', 'do_something_152677' );
function do_something_152677() {
    // Global object containing current admin page
    global $pagenow;
    // If current page is post.php and post isset than query for its post type
    if ('post.php' === $pagenow && isset($_GET['post'])) {
        global $new_current_post_type;
        $new_current_post_type = get_post_type( $_GET['post'] );
    }
}

When pulling this value into cat_slug_goes_here the category does not get updated because the value doesn't match.