and since no one at the time knew what the heck was going on...
was there more than one bomb ?
was there more than one bomber ?
etc....
why did the police refuse to let the crowd leave ?
"why did the police refuse to let the crowd leave ?"
Well, if we let our imaginations run wild with all sorts of frightening terrorist scenarios like many of us did in the months after September 11, we might assume that there was something going on other than an attempt to keep the crowd out of the area where a bomb had just detonated.
I've also read that traces of tularemia have been found on the Mall in DC, after that Cindy Sheehan march. There's a link on Drudge. Seems one of the symptoms of tularemia is "progressive weakness," which is apropos in this particular instance, lol.