What we knew when the police and FBI started responding to the LAX shooting was that someone had walked into one of the terminals and shot several people. What the authorities did was to help the victims, check for a confederate, and secure the scene (Terminal 3), which sounds about right…and hold incoming flights to the whole airport on the ground before they took off, which gave air travel across the country a coronary; divert a couple of arriving flights; stop nearly all departures for most of the day; and make the airport inaccessible to travelers by clogging roads with emergency vehicles. In turn, this crippled the 405 and created hours of stopped and crawling traffic all over the west side. They didn’t know whether they were in the middle of a large coordinated terrorist event; we never know that for sure when a gun goes off (or a CO2 “bomb”).  But they did not have enough evidence that they were, or might be, to justify the chaos they ordained.
It was over the top. It will always be possible for someone to come in the front door of a busy place with a weapon in a piece of baggage or a backpack and shoot people before he or she is stopped. One such incident might be part of a plot reaching out to other airports and other terminals, and might conceivably have something to do with risk to aircraft. But that way madness lies. It would have been wrong to close all the movie theaters in Colorado after Aurora, or stop having marathons after Boston, or shut down the Postal Service after one of its massacres: the shooting at LAX was, and reasonably appeared to be, a one-off, localized outrage. Amplifying the costs to society of events like this on unsupported conjecture about what a fever dream of anxiety could blow it up into does real damage to millions of people and may even increase the likelihood of copycats. I think security services in charge of public places, including airports, need to get a grip. It is not appropriate to bring a city to its knees to demonstrate how risk-averse the various police agencies are.
In contrast, while I’m on this, is the FAA’s mishandling of the small pocket knife issue for travelers. Recall that they announced they would allow pocket knives with blades about the size of a Swiss Army Knife (one of those is really a useful thing to have with you when traveling, for mundane things like peeling an orange or opening a beer or tightening a loose screw in one of your gadgets), and then changed their mind. A knife like that used to be a hijacking device before cockpit doors were secured, but now it’s not. In fact, I would feel much safer if I knew a lot of passengers each had one to help them deal with one or two hijackers who might get something serious through security. If we are willing to go up in the air in an airplane at all, merely to get somewhere, we cannot rationally believe that there is no risk small enough to tolerate for convenience and comfort.