It's not exactly a combat base. Also, massive numbers of military workers are civilian contractors. And even with military people, they often aren't allowed to carry weapons once back home.
My WAG is that it's some sort of planned attack by some dissidents of some sort who chose this as a "military target" they knew would be "soft" and less well protected and NOT full of military men ready to kill them.
Ha ha, remember when Dobbins staged some mannequins in camo and with plastic rifles at the front of the base and freaked commuters out?