public function edit($id)
    {
        try{
            $user = Sentry::findUserById($id);
            //display edit form in non-ajax request
            //
            $this->data['title'] = 'Edit User';
            $this->data['user'] = $user->toArray();

            View::display('@usergroup/user/edit.twig', $this->data);
        }catch(UserNotFoundException $e){
            App::notFound();
        }catch(Exception $e){
            Response::setBody($e->getMessage());
            Response::finalize();
        }
    }