AB's comments were accurate. DC is essentially "no guns allowed" unless you are a cop or criminal. This includes your home or auto. DC is a gun grabber's utopia, with a high rate of armed assault, which of course is blamed on the "easy availability of guns" in MD and Virginia.
MD, where most of the shootings occured, is less restrictive than DC proper, but they prohibit loaded firearms in cars, open carry will result in arrest, and there is no "shall issue" CCW.
Virginia, where 3(IIRC?) shootings occured, is "shall issue" CCW permits and is not much different from the rest of the south in terms of gun ownership.
Also people that live in VA but work in DC or MD would have to leave their guns at home when they commute or any other time they might be traveling north.