These guys are too good to get caught at a road block. By the time the first cop gets the the scene, the shooter could be 5 miles away, by the time road blocks are set up in a 5 mile perimeter, the guys could be 20 miles away heading in the opposite direction, staying off main roads.
All it takes is a VA road atlas and they're one step ahead of the law, all day/night long.
Just as JimRob says loose lips sink ships, I think we need to be equally careful here, especially as news is breaking. Time enough tomorrow to read about and discuss where the roadblocks were.