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 was under 24-hour armed guard at the hospital Sunday after being shot four times, the official said. He was sedated for medical reasons, the official said, adding that one gunshot to the mouth blew a molar out of his jaw.
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, pulled a .223-caliber assault rifle from his duffel bag and fired repeatedly at 39-year-old TSA officer Gerardo I. Hernandez. He turned back to see Hernandez move and returned to finish him off, 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 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 shooter's duffel bag contained a handwritten letter signed by Ciancia stating he'd "made the conscious decision to try to kill" multiple TSA employees and that he wanted to "instill fear in their traitorous minds," FBI Agent in Charge David L. Bowdich said.
"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.
The FBI has served a search warrant on a Sun Valley residence where Ciancia lived, Ari Dekofsky, a spokeswoman for the FBI's Los Angeles field office, said Sunday. Agents are still interviewing people, she said.