The FBI said he had a handwritten letter, stating that he made the conscious decision to try to kill multiple TSA officers and "instill fear in your traitorous minds."
The unemployed motorcycle mechanic who recently moved to Los Angeles from the small, blue-collar town of Pennsville, N.J., had a friend drop him at LAX on Friday just moments before he pulled a .223-caliber assault rifle from his duffel bag and opened fire, killing one TSA officer and wounding three other people, including two more TSA workers.
Officials do not believe that the friend knew of the shooter's plans. Ciancia arrived at the airport in a black Hyundai and was not a ticketed passenger.
Ciancia is facing charges of murder of a federal officer and committing violence at an international airport. The charges could qualify him for the death penalty. It was not immediately clear when he would make a first court appearance given his medical condition.
In court documents and interviews, authorities spelled out a chilling chain of events, saying Ciancia walked into the airport's Terminal 3, pulled the assault rifle from his duffel bag and fired repeatedly at 39-year-old TSA officer Gerardo I. Hernandez. He went up an escalator, turned back to see Hernandez move and returned to shoot him again, according to surveillance video reviewed by investigators.
He then fired on two other uniformed TSA employees and an airline passenger, who all were wounded, as he moved methodically through the security checkpoint to the passenger gate area before airport police shot him as panicked travelers hid in stores and restaurants.
It wasn't clear why Ciancia targeted TSA officers, but what he left behind indicated he was willing to kill any of them that crossed his path, authorities revealed.
The letter in his duffel bag refers to how Ciancia believed his constitutional rights were being violated by TSA searches and that he's a "pissed-off patriot" upset at former Department of Homeland Security Secretary Janet Napolitano.
"Black, white, yellow, brown, I don't discriminate," the note read, according to a paraphrase by a law enforcement official briefed on the investigation. The official spoke on the condition of anonymity because he was not authorized to speak publicly.
The screed also mentioned "fiat currency" and "NWO," possible references to the New World Order, a conspiracy theory that foresees a totalitarian one-world government.
The letter also talked about "how easy it is to get a gun into the airport," the law enforcement official said.
When searched, the suspect had five 30-round magazines, and his bag contained hundreds more rounds in boxes.
U.S. Rep. Michael McCaul, R-Texas, chairman of the House Homeland Security Committee, said on CNN's State of the Union on Sunday that Ciancia's actions show how difficult it is to protect travelers at a massive airport such as LAX.
The terminals are open and easily accessible to thousands of people who arrive at large sliding glass doors via a broad ring road that fronts the facility and is designed to move people along quickly.
"It's like a shopping mall outside the perimeter, it's almost like an open shopping mall," McCaul said.