This was apparently not a terrorist incident. A man picked up the two men in drag and they spent the night partying at a motel. The two ingrates then stole their benefactor’s SUV and somehow managed to get entangled with security officers at NSA headquarters. The case is eerily similar to the Miriam Carey case in DC (here and here).
Here, too, the driver of the vehicle drove up to the NSA entrance, apparently by mistake. The driver allegedly failed to obey orders to stop, and “barriers were deployed," according to an NSA statement. Another part of the statement, or perhaps it is a different NSA statement, says that the car "accelerated toward an NSA police car blocking the road.”