Hmmmmmmmm....intriguing.
The only problem with this theory is that most real estate agents do not drive white commercial vans.
However, it does seem likely that he/they are not exfiltrating the area.
My theory is that he lives in the Aspen Hill area. The first series of shooting are clustered in that area. After hearing the reports of "geographic profiling" and "black helicopters", he tried to throw them off his trail by fanning out over a larger area. As the evidence shows, he is adapting to what the police are doing and the media are ignorantly reporting.
On Tuesday, he was back in the Aspen Hill area VERY early in the morning (but late enough to not alert his family/neighbors by seeming to be only leaving for work). The crime scenes away from Aspen Hill were done later in the day (or at night as in the case of Charlot, Meyers, Franklin and the unidentified man from the Ponderosa Steak House).
I still think the shooter is a heating and air conditioning (or plumbing) contractor. Either the owner or a manager with access to all the keys. When I worked for such a company in the 1990's, we had "box" trucks for the equipment installers, smaller Chevy Astro vans for the PM (preventative maintenance) guys and full sized Ford Econoline vans for the service techs.
Additionally, these types of individuals/vehicles are seen on the road all day and would not arouse the suspicion of the locals. Also, as a tech, he would know the entire service area very well. He would know the short cuts to avoid highly congested traffic areas (that are being blocked and searched by the police). Time is money and he needs to learn how to get to the next service call quickly. I used to know how to avoid these areas (like heavily travelled US Highways, State Roads or I-95) in favor of backroads and "short cuts". He can shoot and then go to his first call of the day in the area and wait for the roadblocks to end.
So Ms. Alphabet Agent (referring to the analyst reading these posts) - cross reference heating and air contractors living and/or working in the Aspen Hill area with the list of owners of .22x chambered weapons from the 4473's being gathered and you will have you man/men.