Sort of. The shootings have been located near major highways that would be busy during rush hours. But the shootings themselves have been in areas where there were few witnesses. The guy mowing the lawn... parking lots (a few people maybe but not tons), the boy was dropped off early for school, few people there.
As a side note, I don't know who the spokesperson was for the school today, but she said the shooting was at 8:09 and that he was there about a half hour early, and that school started between 8:00 and 8:30. She didn't give an exact time for the start of the school day. She left that vague, good for her!
Not so, not at all correct.
The guy was mowing on Rockville Pike, one of the busiest rush-hour roads in Montgomery County.
Aspen Hill (the taxi driver) is at the intersection of Connecticut and Georgia Avenues, both main commuting thoroughfares (and ridiculously crowded at 8:30AM).
Back down to White Flint for Thursday victim #4 and you are still in a dense suburban traffic situation, even at 9:30AM.
Yesterday's shooting was at Rt. 197 and Rt. 50 (two major commuting roads), and just in front of the Bowie tract neighborhood (several thousand homes), again during prime morning rush hour.
My point is that the shooter would have to stay inside the vehicle to do these shootings, and that the vehicle itself would have to be completely inconspicuous. It is simply not plausible that he/they exited the vehicle to do the shooting. Contrary to what you state, there would be dozens of witnesses in the areas described above.
So then you must ask what type of vehicle (a) is completely inconspicuous and (b) allows the shooter to aim and fire with no complications.
My theory: minivan, blacked out windows, sliding door.