I can’t help but think that the tragedy today will, in the long-run, be nothing compared to what could come. How easy/difficult would it be for a guy to stick a nuclear weapon in a suitcase and set it off in front of the White House? How small can a powerful nuke be? How vulnerable are we?
This was addressed back in the 70s by John McPhee in his book, <i>The Curve of Binding Energy</i>. AFAIK, most of the info in the book is still accurate – in fact, it’s probably easier today, what with an extra 30 years or so of people being trained in nuclear physics & engineering, and the increased availability of nuclear material (especially with the collapse of the old Soviet Union).
One scene in this book includes the author and Ted Taylor (one of the US’s top nuke designers) touring the World Trade Center (under construction at the time), talking about what kind of nuke it’d take to bring it down.