False reports of gunfire at Los Angeles International Airport sent panicked passengers running from terminals and onto the tarmac on Sunday night.
Police responded to 911 calls of shots fired at the airport but later said the reports were unfounded and there had been no gunfire or injuries.
"Reports of a shooting incident at LAX have been proven to be loud noises only," the Los Angeles Police Department said about 45 minutes after the reports sparked chaos at the airport.
Multiple 911 calls came in from several locations at the airport about gunfire at around 8:45 p.m. local time (11:45 p.m. ET), several law-enforcement sources told NBC News. They said the calls came from terminals 4, 7, and 8.
People poured out of Terminal 4 onto the tarmac, and a security officer was overheard saying "shots fired." One person told NBC News she heard "pops" in Terminal 4, while others recounted hearing shouts of "run!"
Video posted on Twitter showed people fleeing a terminal and a TSA agent helping up one person who fell.
"We were on the jetway and someone starts pushing behind us," Jon Landis, a sales representative from Boston who was boarding a flight home, told The Associated Press. "One man was frantic saying there was a shooter."
Los Angeles International Airport said the departures and arrival areas of the central terminal area were closed amid the chaos; around 23 flights were diverted during a 30-minute ground stop.
Corey Rosenbusch was relaxing inside a terminal club on a layover when the lights went off and the staff told everyone to shelter in place.
"People immediately started looking at social media, where they saw reports that there was an active shooter," Rosenbusch told the AP.
Officers conducted two sweeps of the airport, including one with K-9s late Sunday, airport police spokeswoman Alicia Hernandez said. She said passengers had self-evacuated and were not ordered to do so by airport police, contradicting reports on social media.
By 11:00 p.m., all terminals of the airport had been reopened and passengers were again proceeding through federal security, airport spokeswoman Nancy Suey Castles said.
Adding to the confusion, a man dressed in a Zorro costume was detained at the airport around the same time of the panic, law enforcement sources said. It was not clear whether the person in any way contributed to the chaos or 911 calls.
Traffic was backed up leading to the airport as police initially responded, and for hours after.
Earlier this month a false report about shots fired at New York's John F. Kennedy International Airport sparked chaos, sending passengers running for cover. Officials later said the sounds of cheers from people watching the Olympic Games may have been confused for gunshots.
The Los Angeles airport was the scene of a real shooting, though, in 2013 when a gunman opened fire and killed a Transportation Security Administration officer. Alleged gunman Paul Anthony Ciancia wounded two other TSA agents and another person in the rampage. He was shot and wounded by police at the airport but survived.