According to court documents, he had a handwritten note saying he wanted to “instill fear” in the “traitorous minds” of T.S.A. agents, and he mentioned conspiracy theories. It is not known whether Mr. Ciancia has a mental illness, but there is no divorcing this incident from the broader context of the nation’s gun problem. That he went on a shooting rampage at an airport is largely incidental; the problem is that he had easy access to a firearm.

If every shooting in a public place led to a new class of law enforcement officers, America would look like a war zone. We would have armed ticket-takers at movie theaters, armed clerks at malls and armed teachers at schools. That’s an outcome the National Rifle Association would love, but that should worry anyone who doubts that more guns are the only answer.