Like what?
a) Purchase guns?
b) Ride the Metro (from East Falls Church)?
c) Impound cars parked in Metro parking lots?
Of note, I simply cannot fathom how he even got the gun into DC because not only is it
illegal to carry handguns in DC, and the gun and magazines he had were
illegal per se in DC, it is also
illegal to carry a gun onto the Metro (even though there aren't any metal detectors and backpacks are VERY rarely checked.)
OBVIOUSLY we didn't pass enough laws to stop him. The only solution is to make what he did EVEN MORE illegal.