That's the title...
http://www.samharris.org/blog/item/the-riddle-of-the-gun (http://www.samharris.org/blog/item/the-riddle-of-the-gun)
And the subsequent article.
http://www.samharris.org/blog/item/faq-on-violence (http://www.samharris.org/blog/item/faq-on-violence)