Combining this with a possible ME terrorist situation, I wonder if this map pattern looks like anything in Arabic.
My guess is that there is no pattern on the map but rather they wanted to get out of town after the heat went up from the school shooting just like they went to Virginia last Friday after the Thursday spree. I think they chose West of DC because they haven't been that way yet. Going to a relatively unaffected area would be safer for the shooter and have easier targets who weren't as cautious.