I’m retired Air Force...can’t speak for Ft Hood, but I travel to military bases in the mid-Atlantic region on a weekly basis in my civilian job. Getting on base (typically) requires a military ID card and a DoD decal on your car. You present the card to the security guard (typically civilian) at the gate, and he waves you through.
If you don’t have the ID card and decal, you must pass through the visitor’s center. Before receiving a temporary pass, you must present your driver’s license, vehicle registration and proof of insurance. You must also have a valid reason for being on base and the MP/security guard behind the desk often calls your destination to confirm that you are expected at that location.
A few caveats; first, the Air Force no longer requires DoD decals on vehicles, since all are stopped/inspected prior to entry. Secondly, it would be relatively easy to forge older-style ID cards, like those carried by retirees; the newer Common Access Cards (CAC), which contain a computer chip, would be more difficult to forge, but not impossible.
Third, the perimeter of any military installation is not 100% airtight. There are miles of fenceline, and gaps in patrols, sensor fields, etc. And, if you have “inside” help, it’s that much easier to pull off this type of attack.
Finally, FBI sources are tellling Catherine Herridge of FNC that terrorism is “not involved” in this shooting. For whatever that’s worth.
I was working on the Acadamy in CO Springs this summer. They had civilians at the gate with side arms and AF people at the entrance to the cadet area with M-4s. Very cool place to work.