[bonesmccoy]

No there is another...
Dirigibles ... if the weather is good, you can put up a dirigible loaded with cameras. Put remote control stations in DC and fly the dirigibles over Bethesda, McLean, DC area.

[Boiler Plate]

Another solution that is already in place are the traffic cameras used to report traffic.

[El Gato]

Doesn't the area have traffic cams all over the place like many urban areas are getting. I know they are down to what don't even qualify as "major" intersections in San Antonio. The guy or guys are probably on all sorts of surveillance video already. It's just that they or their vehicle(s) don't look especially unusual, nor have they been caught in the act of shooting, and if they stick to wooded areas, inside vehicles and such, they probably won't be caught on the videos either.