At this point, the sniper could be a lone nut-case. He could be Al-Quaeda. He could be Iraqi military. He could be more than one person, and he could be a she.
The point is, ANY of the above theories are legitimate--none are either proved or disproved.
But the conviction, CIA letter, and current terrorism (in the DC area) are a rather interesting co-incidence, are they not?
This person or people who are doing these shootings have shot 12 people without anybody getting so much as a license plate number or a decent description. They have to be pro(s). Nobody is that good their first time out.