Don’t know if they were inside. All the article says is at. They could have been walking to/from their car.
True enough. You need a bunch of codes and clearances to even get into that kind of building. This, of course, assumes that they are talking about what I think they are and not just the base quarterdeck area.
But to get on base the person would need either a ID or to be with someone who had one. I would be looking for more than one perp if I was CGIS.