Not only that, but the immediate security - i.e. how he got his weapons on base? Could it be that rent a cops are not really a very good idea?
I saw his car being towed OFF the base. I assume that he drove onto the base like everybody else.
IOW, he could have had an RPG in the trunk, if he had an RPG.
He was driving a rental car, which the guards know are insured, so he would have been waved thru the outer gate or he could have gotten a temporary pass for the car easily. It is quick and easy to break the barrel off of a Remington 870 so the shotgun could have been in a package no longer than a foot and a half and that, in turn, could have fit in a brief case, etc. It was mentioned that he came out of a wash room firing so he could have been in a stall getting his gear working. Remember that this is partially an industrial area so people carry all sorts of stuff pretty much un-noticed or un-cared about.
And he drove a rented Prius, which has a “tonneau” cover in the hatchback. They should have made him unroll it to get on base. But I thought the gates were handled by Marines?