Here is a short interview Butcher did with NPR: http://www.wnyc.org/story/princip-pulled-the-trigger-but-never-meant-to-start-a-war/ 

And here’s a long-form printed interview: http://www.joshirby.com/2014/06/23/gavrilo-princip-weaponized-history-and-the-role-of-the-historian-interview-with-award-winning-author-tim-butcher-on-his-new-book-the-trigger/