These things take place partly because when Bill Clinton was in office he disarmed our military on base. Wouldn't allow them to carry guns. He turned our military bases into "gun free zones". Or as I call them "shooting gallerys".
No deterrents. Free fire zones.
If you're ever in a situation like this. Don't do what authorities tell you to do, don't shelter in place. Get the hell out. Run for your life. Save your life.