LOS ANGELES (CNN) -- Witnesses to a gunman's mayhem at Los Angeles International Airport are providing the first possible clues to what motivated the attack.
"Hey, are you TSA?" some heard the alleged shooter, 23-year-old Paul Anthony Ciancia, ask.
As travelers answered "no," that they did not work for the Transportation Security Administration, the gunman would move on.
Leon Saryan was one of those questioned. He told CNN's Anderson Cooper that the man he'd just seen shoot a TSA officer "calmly" walked toward him and asked, "TSA?"
"I just shook my head," Saryan said. "And he kept going."
Whatever the reason, the suspect, armed with what police say was an assault rifle, opened fire in Los Angeles International Airport's Terminal 3, killing one and sending dozens scattering before he was wounded and captured.
He had enough ammunition to "have literally killed everyone in that terminal," Los Angeles Mayor Eric Garcetti said.
Investigators were digging into his background to find out clues about his motives.
Source: Angry, rambling texts
The materials found on the suspect included a rant that appeared to refer to the New World Order as well as anti-TSA and anti-government claims, a federal law enforcement official said Saturday.
It's not clear what gave rise to the references, and federal investigators have found no known links to known groups or anything in the suspect's background to explain them. The New World Order is generally considered to be a conspiracy theory in which people suspect a group of elites is conspiring to form an authoritarian, one-world government.
The incident disrupted flights and inconvenienced passengers. As of Saturday morning, Terminal 3 remained closed, and it was unclear when it would reopen.
In a message on Twitter on Saturday morning, the airport said that from the start of the incident around 9:30 am Friday through midnight, an estimated 1,550 scheduled flights with about 167,050 passengers were "impacted."
Travelers who abandoned bags in the terminal amid the shooting will not get their belongings back until the FBI has completed its investigation and reopened the terminal for public use, the airport said.
The effects of the shooting are being felt on the opposite coast, where the Port Authority of New York and New Jersey increased patrols.
A TSA officer killed
The TSA said Gerardo Hernandez, who would have turned 40 next week, was shot and killed -- the first employee of that relatively new agency to be slain in the line of duty. He was working as a travel document checker at the time, TSA workers' union and federal sources say.
Two other TSA officers were also shot, one in the leg, authorities said.
TSA: Number of guns discovered in airports rising
The suspected gunman was detained after being shot in the chest multiple times, according to an intelligence source briefed by Los Angeles police. As of Friday evening, he was receiving medical attention at a hospital, according to FBI Special Agent in Charge David Bowdich.
Ronald Reagan UCLA Medical Center said that it received three male victims -- one in critical condition and two in fair condition. One of the two in fair condition suffered gunshot wounds, while another had an unspecified injury, said Dr. Lynne McCullough, an emergency physician at the Los Angeles hospital. One of them had been released by Friday afternoon; one of the others who remained at the hospital was Ciancia, according to the intelligence source.
Two other patients were transported to Harbor-UCLA Medical Center in Torrance, said David Klurad, a trauma surgeon there.
Klurad described one 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.
Another clue to Ciancia's state of mind came from his family. He lives in Los Angeles, but his family back in New Jersey were concerned about him, said Allen Cummings, chief of police in Pennsville, New Jersey.
Ciancia's family became concerned in recent days after he sent his brother and father "angry, rambling" texts venting about the government, living in Los Angeles and his unhappiness generally, an intelligence source said.
Opinion: Arming TSA officers not the answer
But despite the unsettling text, Ciancia's family was still surprised by Friday's events.
"They're upset," Cummings told reporters. "I mean this is a shock to them, it's a shock to our community."
Terror in the terminal
Transportation Security Administration:
-Agency was established in the wake of 9/11. Responsibility for civil aviation security was shifted from the Federal Aviation Administration to the TSA.
- The TSA employs nearly 50,000 security officers, inspectors, air marshals and managers.
-They screen more than 1.8 million passengers each day at more than 450 airports nationwide.
-Since the agency's inception, the TSA has screened more than 4 billion checked bags for explosives.
-Depending on their pay grade, TSA employees can make between $17,000 and $155,000.
The shooting caused what airport police Chief Patrick Gannon 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 said. "Nobody really knew what was going on."
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.
Saryan, the passenger who saw the gunman, had just cleared the TSA checkpoint and was reaching for his shoes and belt when shots rang out, prompting "everybody (to) hit the ground and ... run." A TSA officer grabbed Saryan's shoes and started running alongside him, before the gunman grazed the officer with a bullet.
"I went and cowered in a corner," Saryan said.
The suspect kept moving down Terminal 3, carrying three magazines for his weapon, according to the intelligence source briefed by Los Angeles police. He began running down Terminal 3.
He had company. Gannon said two officers from his department responded "within seconds after the shooting started" and ran off in pursuit of the suspect.
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 it was safer there.
The bloodshed finally ended when law enforcement shot the gunman in the circular area where Cardenas had been, the intelligence source said. They didn't take any chances with the wounded suspect either, handcuffing him to a gurney as he was carried out. Authorities said they found more than 100 rounds of unspent ammunition.
The gunfire was so unexpected and sudden that many panicked passengers left their belongings as they ran out of the terminal to safety.
LAX officials tweeted that passengers would be able to return sometime Saturday to pick up the items they discarded in the chaos