Sammy JS forcing a notFound

Question

I'm currently trying to force a notFound response when certain parameters are met in sammy js:

this.get('#/projects/:url', function(){
            $.ajax({
                type: "POST",
                url: 'package.php',
                data: {
                    'url-verify': this.params['url']
                },
                success: function(data){
                    if(data.success)
                    {
                        this.load('page.php?='+this.params['url'])
                        .swap();
                    }
                    else
                    {
                        //force 404
                    }
                }
            });

        });

I already have the code set up if a notFound were to be present, but the issue is how do I force a "notFound" if, in my case above, the feedback for the AJAX comes back with an error?