[Eala]

2) 18 urban areas have a population greater than D.C. What are the odds that a domestic crazy would pop up in D.C. instead of one of the other areas with a greater population density? 1 in 19?

I suspect too high a population density would work against this form of attack (as opposed to, say, a car bomb).

[Jeff Head]

Actually, to the contrary, a high density population area works to their favor. For the trained operative with the right equipment, it is easy for them to blend in after the fact.

In a more rural area, their car coming and going, their presence getting to and from the "shoot" are all more likely to draw much more attention than in a highly populated area.

So, if they are cool or "professional" (hte to use that word) enough about it, they are in fact benifited in this kind of operation by higher population density IMHO. All they have to do is conceal the shot from a sound and site perspective ... which they appear to be doing quite well.