(ABC News) -- The 23-year-old suspect charged in carrying out a shooting rampage at Los Angeles International Airport has told authorities that he acted alone.
Paul Ciancia, who is under heavy sedation and monitoring at the hospital after being shot by airport police, told law enforcement officials he had been dropped off at LAX's Terminal 3, the Associated Press reported.
Federal prosecutors charged Ciancia with murder of a federal officer and commission of violence at an international airport on Saturday evening. Both charges are potentially punishable by life in prison or the death penalty.
On Friday, Ciancia shot a Transportation Security Administration officer, Gerardo I. Hernandez, at point-blank range, left the scene and then returned to shoot him again after Hernandez was seen moving on a surveillance video, the officials said. Hernandez later died. Ciancia is also accused of shooting two other TSA employees and a civilian, and causing other injuries.
Ciancia wrote in a signed note he carried with him to the airport that he targeted TSA officials and "made the conscious decision to try to kill" because he wanted to "instill fear in your traitorous minds," according to a federal affidavit outlining the charges against him.
"He targeted, specifically, TSA officers," FBI Special Agent in Charge David L. Bowdich told reporters this evening. "His intent was very very clear in his note."
In addition to the note and eyewitness accounts, investigators have surveillance video of the shootings, Bowdich said, and they are seeking additional digital media evidence potentially gathered by civilians at the airport. Such evidence or information can be submitted at https://laxshootingtips.fbi.gov.
However, investigators said Saturday that they have not been able to speak directly with Ciancia because of wounds he suffered as he was subdued.
"He is receiving medical treatment," Bowdich said. "I'm not going to talk about his gunshot wounds. At the moment, he is unresponsive and we are unable to talk to him, as of today."
Bowdich credited a swift law enforcement response for preventing further carnage.
"They did stop this before, we believe, it would have been a much more grave action to include additional casualties," Bowdich said.
According to the affidavit, "at approximately 9:20 a.m. [PT Friday], Ciancia entered Terminal 3 at LAX and approached the Transportation Security Administration checkpoint. Ciancia pulled a Smith & Wesson .223 caliber M&P-15 assault rifle out of his bag and fired multiple rounds at point-blank range at a TSA officer [Hernandez] who was then on duty and in uniform, wounding the officer. Ciancia began to walk up an escalator, looked back at the wounded officer, who in video appeared to move, and returned to shoot the wounded officer again. The TSA officer was fatally wounded.
"Ciancia then fired his weapon on at least two other uniformed, on-duty TSA employees and one civilian passenger, all of whom sustained gunshot wounds," the affidavit added. "Ciancia was pursued and shot by a sergeant and an officer of the Los Angeles Airport Police."
Besides those shot, two civilians suffered what Bowdich described as "evasion injuries" caused by efforts to escape once the shooting erupted.
The shooting sent hundreds of passengers streaming out of the terminal, with many fleeing onto the airport runway. Dozens of flights to and from the airport were delayed or canceled as a "tactical alert" was triggered for the Los Angeles Police Department.
Witnesses described a chaotic scene, as many ducked for cover inside bathroom stalls or dropped to the floor upon officers' commands.
"I heard gunshots, and a few seconds later, I saw him coming up the elevator and walked by about 10 feet away from me with his gun pointed," Andrea Trujillo, who was at the terminal when shots first rang out, told ABC News.
Jose Martes, who was at the airport with his wife, Miriam Rodrigez, awaiting a flight to Norman, Okla., said he didn't realize what was happening at first.
"There was a loud bang. At first we looked at each other and everyone in line. We're like, OK, nothing unusual," he told ABC News. "We thought it was something else, but from, like a couple of seconds from that, that's when we heard just straight shots going down. That's when we all fell to the ground and we knew that this was not a test."
Authorities said Ciancia was able to make it all the way to the back of the terminal, near the departure gate, before he was shot down by officers and taken into custody, according to Mayor Eric Garcetti.
As law enforcement officials work to uncover Ciancia's motivations, the note found at the scene indicated Ciancia's anti-government sentiments and suggested that he expected to die in the airport shootout.
The note ended with the letters "NWO," according to law enforcement sources, which is believed to stand for "New World Order." The note also specifically mentioned anger and frustration targeted toward the TSA.
Ciancia's family was also concerned for his well-being. Ciancia's father contacted police in Pennsville, N.J., on Friday with the concern that his son may be suicidal, Chief Allen Cummings of the Pennsville Police Department told ABC News.
"Their younger child got a text message from Paul stating that there were some comments in there about his well-being, and he wanted to possibly take his own life," Cummings said.
Cummings said he called the LAPD today and asked for officers to "try to get a well-being check" on Ciancia.
Officers went to Ciancia's apartment in Los Angeles before the shooting and talked to his roommates, Cummings said.
"He was a really nice guy," one of his roommates told ABC News. "A little introverted, but nothing I would ever, ever expect him to do."
Ciancia was believed to be from Pennsville, N.J., however authorities said he had a residence in Los Angeles. Overnight, officials searched both his East Coast and West Coast residences.
Witnesses described Ciancia as a short, young, white man, carrying a long-rifle.
One of the shooting victims was a TSA officer who died of his wounds. The officer was a behavioral detection officer, assigned to identify passengers acting strangely, said J. David Cox, president of the AFGE, the officers' union.
The TSA confirmed the identity of the officer killed as Hernandez, 39, who has been with the TSA since 2010.
The officer is the first TSA employee to be killed in the line of duty.
"It's a sad occasion," Cox said.
Six people were injured, including three TSA officers. Five were taken to nearby hospitals.
"One arrived in critical condition and two are listed in fair condition," a spokesman from Ronald Reagan UCLA Medical Center said in a statement.
An emergency physician said the patients suffered bullet wounds and other injuries. Two other patients were taken to other hospitals.
"No words can explain the horror that we experienced," TSA Administrator John Pistole said in a statement.
ABC News' Cecilia Vega and Pierre Thomas
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