A man armed with what police say was an assault rifle and carrying materials expressing anti-government sentiment opened fire Friday morning at Los Angeles International Airport, killing one person before being chased down himself, authorities said.

Eyewitnesses said the suspect asked people, “Hey, are you TSA?” — the acronym for the Transportation Security Administration — according to a federal law enforcement official. If they said “no,” he would move on.

In the aftermath of the shooting, investigators found information on the suspect expressing not just anti-federal government sentiment but also anger at the TSA specifically, according to the federal law enforcement official.

By then, a TSA officer was dead — the first employee of that relatively new agency to be killed in the line of duty, according to American Federation of Government Employees president J. David Cox. At least one other TSA employee had been shot in the leg, according to a former Los Angeles Police Department ranking officer who was briefed by investigators.

The suspected gunman himself was detained after being shot in the chest multiple times, according to an intelligence source briefed by Los Angeles police.

He was identified later by the FBI as Paul Anthony Ciancia, a 23-year-old from Los Angeles. Law enforcement sources told CNN that, in addition to the southern California city, the suspect also had an address in New Jersey.

Ronald Reagan UCLA Medical Center said that, hours after the incident, it received three male victims — one in critical condition and two in fair condition. One of the two in fair condition suffered gunshot wounds, another suffered an unspecified injury, said Dr. Lynne McCullough, an emergency physician at the Los Angeles hospital.

Two patients were transported to Harbor-UCLA Medical Center in Torrance, said David Klurad, a trauma surgeon there.

One was what Klurad described as a “middle-aged” person with minor injuries from being shot in the shoulder. The other had no signs of life when he arrived at the hospital, the surgeon added. It wasn’t known if this person was the slain TSA officer.

The episode caused what airport police Chief Patrick Gannon, who had said the shooter used an “assault rifle,” described as a “large amount of chaos.” People ran for their lives and took shelter wherever they could as authorities pursued the gunman.

Chuck Ocheret was among those in the busy airport when he heard two “loud pops.”

“Then I heard this mad rush of people, and there was a stampede of people coming from this direction,” Ocheret told CNN. “Nobody really knew what was going on.”

Still, by Friday afternoon, authorities believes the worst was over. Gannon noted it is believed there was only one shooter.

Source: Gunman had 3 magazines for weapon

An otherwise normal day in the airport’s Terminal 3 turned upside down around 9:20 a.m. (12:20 p.m. ET), as the suspect approached a checkpoint.

There, he “pulled an assault rifle out of a bag and began to open fire,” Gannon said.

The suspect didn’t stop there. Equipped with three magazines for his weapon, according to the intelligence source briefed by Los Angeles police, he began running down Terminal 3.

Traveler Vernon Cardenas was sitting at one end of the terminal, when he heard noise and saw a mass of people running toward him. He and others bolted through a kicked-open exit door and ran onto the tarmac — believing then it was safer there — even with then still-arriving and departing jetliners — than in the concourse above.

The circular area where Cardenas had been is where the bloodshed finally ended with the gunman’s shooting by law enforcement, according to the intelligence source.

Actor Tim Daly said that when he was eventually led out of the the Virgin America first-class lounge, he saw where the incident came to a head around Gates 35 and 36. After being told not to step on any blood or glass, Daly spotted a high-powered rifle on the ground along with three magazines, a pair of black shoes and several bags strewn across the floor.

The episode soon rendered one of the world’s busiest airports a ghost town. Large portions were evacuated as authorities ordered a “ground stop” for arriving places, said police and the Federal Aviation Administration.

Almost every flight scheduled to leave the airport on Friday will be “significantly late,” said Gina Marie Lindsay, executive director of Los Angeles World Airports.

The area around the airport was jammed with cars as police shut down access to the airport.

The airport was still accepting incoming flights, but doing so at less than half the normal rate as a few were rerouted, Lindsay said. Some flights that did arrive sat on the tarmac as the investigation continued.

Police at Los Angeles International Airport announced around 2 p.m. over a loudspeaker that they were going to start allowing workers back into the airport so operations such as processing incoming and outbound flights could resume.

The “ground stop” was expected to finally lift two hours later, the airport tweeted — though even then, hordes of people still lingered on sidewalks outside the airport, with nowhere else to go.

But even when flights resume, parts of Terminal 3 will still be off limits, with flights that were supposed to go in and out of there moved to other terminals in the massive airport.

‘Mayhem is the best I can describe it’

That means travelers essentially had nowhere to go for nearly seven hours, far worse than even the most infuriating of Los Angeles’ epic traffic jams.

Still, the waiting was welcome relative to the pandemonium hours earlier — when Robert Perez told CNN affiliate KCAL/KCBS that people started diving for cover and scores rushed down a staircase.

Recalled Perez: “Everybody started to panic.”

Alex Neumann described the scene as “mayhem,” as people ran and, in some cases, got knocked down.

Even once the suspect was shot and detained, law enforcement officers roamed the airport with guns drawn in search of possible other culprits.

KCAL showed live video of three officers with rifles to their shoulders inspecting parked cars in an open-air parking lot.

At one point, firefighters lay tarps on the street at the airport, apparently for triage. Several ambulances were at the airport, and at least one person was loaded into one.

A U.S. intelligence official “doesn’t see any indications of terrorism” in Friday’s shooting. The intelligence community has been in “constant contact with a range of law enforcement authorities,” according to the official.

President Barack Obama was briefed on the shooting and will continue to be updated, spokesman Jay Carney said. Obama later addressed the issue later while meeting with Iraq’s prime minister, saying he was concerned about the shooting.

Authorities were interviewing about 100 witness, the intelligence source said.

A leader of the union representing TSA officers deplored the incident.

“We are sickened by reports of today’s shooting,” Cox said.