On Saturday, President Obama said of the killings, "This is not normal. We can't let it become normal." Obama was incorrect: The very sad fact is that it is normal, in the sense that these events have become commonplace and the nation has become desensitized to them. In the three years since the Sandy Hook school shooting in December 2012, there have been around 80,000 gun deaths, at least 142 school shootings, and about a thousand mass shootings. Our response to this carnage has been mostly hand-wringing. Gun rights advocates say there is anecdotal evidence that guns in the hands of "good guys" would have stopped this "bad guy." Last Friday's shooting is one more in a staggering number of anecdotes where a deranged, determined killer succeeds in holding off a well-armed, well-trained police force. If dozens of cops can't stop a killer, how would the rest of us do so?