No, he's not joking.
The first armed responders to show up at the Fort Hood shooting were civilian base police.
Aaron Alexis wasn't confronted with serious armed resistance until civilian police showed up -- just one guard that he apparently got the jump on.
Tennesee armory: "Tennessee National Guard workers managed to take down a shooting suspect and hold him until police arrived..."
Fort Bragg: "Minor said that the gunman, who was firing at them, turned away. And as he did, he and Sgt. Edward Mongold tackled the man. "It was a fight for his life," Minor said. "It was a fight for our lives. Minor, Mongold and several other soldiers disarmed the shooter and held him for the military police.."
Apparently, the military bases in the incidents you linked to are real-life military bases, where for example many guards aren't allowed to load their weapons without specific orders, rather than the bristling-with-weapons-super-high-security-one-false-move-and-you're-dead military bases in your imagination.
True, some parts of military bases ARE exactly like you imagine. That's not where shootings have tended to happen, though, for obvious reasons.