LOS ANGELES - The man accused of opening fire at Los Angeles International Airport, shooting employees and terrorizing travelers, accomplished two of his goals, according to authorities: killing a Transportation Security Administration officer and showing how easy it is to get a gun into an airport.

The deadly rampage left investigators to piece together what motivated Paul Ciancia's hatred toward the agency formed to make air travel safer after the Sept. 11 terrorist attacks. But the attack could ultimately lead to changes in the way airports are patrolled.

Ciancia, who was shot four times by airport police, remained in critical condition Monday. He has not been scheduled to appear in court. Any appearance will depend on when his doctors say he's ready, FBI spokeswoman Laura Eimiller said.

The FBI said Ciancia 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 charged with murder of a federal officer and committing violence at an international airport, charges that 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 who 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.