I still think "nut with a gun." Or stupid terrorists. Picture this: terrorists are supposed to be well funded. Have a vehicle, several rifles of various calibers, and money to travel. Assuming individuals willing to do this are difficult to recruit, just have one or two two-man teams. Shoot one person in D.C. then drive non-stop to, say, Austin, Texas and shoot another. The next day, another in Miami, then the next in a small town in South Dakota. Go on from there, with no pattern, and a different rifle used at each, in rotation. Logistically this is easy for two men driving in shifts and would [b]truly[/b] strike terror into the Country. Everyone would be afraid to peek out the door. OTOH, a nut with a gun has only one rifle, one vehicle, and no time/money to travel, so he just shoots in his nearby vicinity, which he knows well.