LOS ANGELES — In the moments before reports of gunshots spread panic at Los Angeles International Airport, police with weapons drawn had confronted a masked man outside a terminal who was carrying a plastic sword and dressed like Zorro.

Authorities have now determined there were no gunshots. The only people at the airport with guns Sunday night were officers, but false reports of an active shooter triggered a ripple of chaos that sent frantic travelers racing to the street and onto the tarmac.

As police tried Monday to sort out the cause of the disruption, experts said the incident — the second of its kind at a major U.S. airport in two weeks — highlights one of the challenges faced by airports at a time of terrorism and frequent unsubstantiated reports.

“You can’t always avoid them, and when they occur you need to respond as if it’s a legitimate attack every single time,” said Anthony Roman, who runs a security consulting firm in Lynbrook, New York. “There are false alarms. There are pranksters who pull fire alarms, and we evacuate right away because we’re all terrified of fire.”