You might be right on the money with this. My working theory is that he's using the weekends to do some recon and scout his next shooting positions...then waiting for rush hour times to mask his getaways. Certainly using a different vehicle for his scouting...and certainly not toting his weapon around with him. The taskforce should be scouring through any and all videos of the Bowie, Manassas and 2nd Fredericksburg shootings from LAST weekend.
If they have a picture - even if a small grainy one from some video in Manassas - I'm shocked that they would not have released either the image or a sketch of the image indicating that the guy is not a suspect - but wanted for questioning. You have everything to gain and nothing to lose.
I find it difficult to imagine that this guy is entering and exiting his van in broad daylight with weapon en tote - except for the Bowie school shooting. My guess is that he's parking with the van positioned so that he can sit in the back corner of the van and shoot out through either the passender or driver's side windows. Maybe even with a sun shade covering the front windshield. That might explain why he shot with a police officer across the street - he simply didn't see the policeman while he was snapping in on his target.
Wonder how long before the hit the cop showed up?? I think that's important as it might determine whether the guy was already in position, whether they are listening to a police radio, whether they are using 2 way radios (assuming there is a spotter).
Assuming neither the shooter or the spotter could see the cop, that might give us a clue as to "where" and "if" the spotter is exiting. The spotter might just go into a restaurant after the operation is complete and wait for a call on his cell phone for "pick me up" details.
Sac
People would be less likely to notice them parked on the side of the road, if they disguised themselves in this manner, and they might be more likely to pass a quick inspection by the police at a roadblock/search, too.