Mass shootings have come to define our nation. Today's shooting at Virginia Tech -- the largest mass shooting in U.S. history -- is only the latest in a continuing series over the past two decades. These tragedies are the inevitable result of the ease with which the firepower necessary to slaughter dozens of innocents can be obtained. We allow virtually anyone the means to turn almost any venue into a battlefield. In the wake of these shootings, too many routinely search for any reason for the tragedy except for the most obvious -- the easy access to increasingly lethal firearms that make mass killings possible.