The ar15.com site mentions a bullet hole in a window that is too big to have come from a .223 round.
The sniper(s) dumped the large white van by now, too hot. Actually, I agree that a large white van probably was not used to begin with, since it is different enough to be relatively easy to spot in a neighborhood should the sniper have had the bad luck to be profiled.
Seems to me, a regular van or SUV would work just fine.
The MO is terrorism of soccer-parent central Eastern seaboard. The most obvious political agenda is the need by the gun grabbers for Congress to pass a bill continuing the '94 Assault Weapon Ban. The primary target of the Assault Weapon Ban was the AR-15 and clones in .223 caliber.
GWB has stated on record that he'll sign a continuance of the '94 AWB if it reaches his desk. As of before these shootings started, it did not look likely that any such bill would have made it past either next year's Senate or House.
So: these shootings are as if they were tailormade to hand losing Democrat members of Congress across the country an issue out of the blue that could rescue their campaigns and throw projected control of Congress back to the Democrats in the next session.
The AR15 has been around since the Vietnam War. Sniper rifles have been around since the Revolutionary War. There have not been many (if any) cases of random sniper terrorism. The question is why now? The underlying question needs to be who benefits?
(And these are the kinds of questions the FBI does not seem to be asking...)