— -- The chaos at Los Angeles International Airport on Sunday night, during which passengers breached security doors and spilled out onto the airport tarmac, was sparked by law enforcement detaining a man in a Zorro costume as well as loud emergency locks that sounded like gunshots, officials told ABC News today.
Panic erupted at the airport after word of a shooting threat spread -- later deemed a false alarm. But the false alarm brought travel to a halt and caused delays to pile up into Monday morning.
According to two officials briefed on the investigation, it began when a street actor in a Zorro costume was at the airport picking up a friend.
Law enforcement at the airport became suspicious of him and detained him to for questioning -- in full view of people moving through the busy Terminal 7. A small crowd saw the questioning and some of those people began rushing away from the area for fear that this was a security incident in progress, the officials said, and one passenger notified a senior TSA official that there was a security incident ongoing in the terminal.
The TSA agent put out calls to other terminals and checkpoints notifying them of an ongoing security incident in Terminal 7, the officials told ABC News.
The mounting panic caused travelers to rush for emergency exits and doors that lead to the tarmac.
Many of the doors have heavy locking mechanisms that make loud noises when they're opened, the officials said, and during the panic, the "boom" sound from the emergency locks were mistaken for gunshots.
Within minutes, travelers were posting on social media and calling in emergency reports of gunshots at the airport.
Airport officers responded and secured all nine terminals in under an hour, LAX said. The scare resulted in evacuations from Terminals 1, 4, 6, 7 and 8, LAX officials said. Police conducted a search, later confirming there was no evidence of any shooting and that the incident appeared to be a false alarm.
Now that officials have a complete picture of what occurred, they are looking to determine if "our own tactics contributed to the panic," one person briefed on the investigation told ABC News.
The officials who described the Sunday night's events to ABC News stressed that the November 2013 incident in which a TSA agent was killed at LAX is still fresh in the minds of all security personnel at the airport, and as a result, the tendency at LAX is to be more proactive in the face of possible security threats.
ABC News contributor Steve Gomez, who oversaw FBI operations at LAX as the former head of counter-terror investigations at the FBI's Los Angeles division, noted that "LAX is known as a terrorist target. Given that, when you have a situation [like Sunday] there’s going to be an immediate law enforcement response."
“Given the nature of the threat to LAX and the circumstances around the world, it’s very important that the information about a potential incident or security incident, that information gets out to everybody," Gomez said.
While “communication has to move quickly,” Gomez said, “government agencies and their representatives have to be mindful of the accuracy of the information that they are passing around."
Travelers should also be mindful of their surroundings if a scare like this one arises. "There are two sections when you get to the airport: one is the area before the screening," Gomez said. "So, when you are arriving at the airport ... there’s a certain point where nobody has really been screened so anything's possible."
Once you go through screening, "You’re in what they call the sterile environment," Gomez said. "You have some comfort that everyone's been screened ... [but] if somebody makes it through with a firearm or an explosive ... you have to be prepared act: run, hide or fight."
Gomez recommends to also be aware of exits while you’re sitting at the gate. “There is a way for you to get out of the area that’ll take you down to the tarmac," he said. "You may be at least out of potential danger from the gate area," but "you have to be careful of where you're running to," because there are still potential dangers like moving vehicles and airplanes, he said.
LAX said enhanced security resources and technology improvements -- adopted after the 2013 deadly shooting -- "dramatically helped law enforcement respond quickly and effectively" to the active shooter false alarm Sunday. LAX said airport police officers responded to the report less than a minute after they were notified.
"Airport officials are holding several reviews to assess the response to Sunday’s incident and continue to improve effectiveness for active-shooter and false-alarm scenarios," LAX said.