The Mall in Columbia was clearly yet another gun free zone. (Click on figure to make it larger.)
Of course, just as important, it is essentially impossible for your average citizen in Maryland to obtain a concealed handgun permit. Permits are issued to ex-cops and a few politically well connected wealth people. With one of the lowest permit issuing rates in the country, criminals and terrorists in Maryland have virtually nothing to worry about in terms of a permit holder stopping them.
For related information on this debate see:
For a very detailed discussion on mass public shootings from 2010 see John Lott’s book “More Guns, Less Crime.”