The Thursday shootings prove that wrong.
It would be impossible to cover the ground of the four Thursday shootings in the 2-hour window of 8:00 to 10:00 AM, and to walk around completely unnoticed in a dense suburban area with a rifle, during rush hour.
That part of Rockville/Kensington is ridiculously crowded during weekday rish hour.
Also, if I recall the intersection of Rt. 50 and 197 (todays shooting) is a huge open area of several acres, and it is probably one of the busier rush hour intersections in that part of Maryland.
IMHO, this could only have been done from a parked vehicle, but parked in such a way as to draw no attention during rush hour. That's kind of hard to figure given where these shootings occurred.
Presumably the police have done their weekend forensics and by now have a pretty good idea of where the shooter was positioned.
I would guess that says a lot about the sort of perp they're dealing with (wouldn't the perp's training and MO show up in a consistent distance, angle, mode of cover, how they position themselves relative to target, etc?)