Obviously, the shooter was not a "gun guy". Anyone with any real interest in firearms knows that DC is a massive "gun-free zone", and that despite Supreme Court decisions to the contrary, the laws against firearms there are incredibly restrictive. Which really only goes to show that criminals, terrorists, and those with serious mental problems don't really care about laws if they are bound and determined to hurt/kill others. The only thing that will stop them, or limit the destruction, continues to be effective armed defense.
An unarmed man can only flee from evil, and evil is not overcome by fleeing from it. --- Colonel Jeff Cooper