According to a link on Drudge, the toll is up to 9. Just keeps getting better and better, eh?
The thing that worries me is that THIS SHOULDN'T HAVE HAPPENED. The CTA here in Chicago runs the same kind of software that's supposed to keep this exact scenario from happening. The software knows where the trains are in relationship to one another and keeps them a minimum distance apart (200 feet here if I remember right). We had an accident about 6 or 7 years ago here where one Brown Line train rear ended another one on elevated tracks and derailed both. In a city where an El car has fallen off the tracks downtown in living memory (I know someone who was in a different car on the same train), that's a pretty big deal. As I understand it, there have to be multiple failures, human, computer and mechanical, to happen.
In places like DC and Chicago (add New York and Boston to that list too), light rail is just the most convenient way to get around the city. In Chicago, a blog called The CTA Tattler basically had a little addendum to their regular post wishing all the DC victims well but making no other note. And I think that's how most regular riders not in DC will feel about it, even though there seems to be a very real possibility that it could happen here.