The suspect in the killing of a TSA screener during a shooting rampage at the Los Angeles International Airport was charged with murder Saturday, and authorities said he had signed a letter to TSA employees saying that he wanted to “instill fear in your traitorous minds.”

Federal prosecutors said Paul Anthony Ciancia, 23, killed TSA screener Gerardo Hernandez during a terrifying outbreak of gunfire Friday in which at least three other people were wounded before police shot Ciancia.

The source of Ciancia’s apparent hostility toward the TSA remained unclear and puzzling. But a statement filed in court by the FBI gave the first detailed account of how the shootings unfolded.

According to the FBI, Ciancia entered the airport’s Terminal 3 about 9:20 a.m. and approached the security checkpoint. Pulling a Smith & Wesson .223-caliber M&P-15 assault rifle from his bag, he fired multiple times at point-blank range at Hernandez, who was on duty and in uniform, leaving the screener wounded.

Then, after starting up an escalator, Ciancia looked back at Hernandez, who appeared to move. Ciancia then went back to shoot him again. the statement said.Hernandez was fatally wounded.

A timeline of events from the LAX TSA shooting

Ciancia then shot at “at least” two more TSA employees and one airline passenger, wounding all three, before two pursuing Los Angeles Airport Police officers wounded him, the FBI said.

In a bag that Ciancia had at the airport, the FBI said, other law enforcement officers found a handwritten letter, signed by the suspect, saying that he had “made the conscious decision to try to kill” TSA employees. Ciancia’s possessions at the scene “included five magazine clips” of ammunition.

Ciancia was taken to a hospital; an FBI spokesman said no information about his condition was being released Saturday night.

The gunfire sent panic through the nation’s third-busiest airport and disrupted air traffic there along with the travel plans of thousands of would-be passengers throughout the nation. The airport was fully reopened on Saturday afternoon, authorities said.

On Saturday, Hernandez’s wife spoke to reporters outside her Los Angeles area home, describing him as a “wonderful husband, father, brother, son and friend.”

She said her husband, who was about to turn 40, had come to the United States at age 15 from El Salvador and “took pride in his duty for the American public.”

Still unclear Saturday was what had led Ciancia to make the TSA his alleged target, but there were signs of psychological trouble. According to an account from police in the New Jersey town where he grew up, Ciancia had sent a text message to his brother indicating that he might harm himself.

As investigators search for a motive in the shooting at LAX, friends and neighbors of the TSA agent killed remain in disbelief. (Reuters)

The message had aroused enough concern to prompt his father on Friday to get authorities to check on him in Los Angeles, where he was living.

“I understand that they tried to reach him,” said a neighbor of Ciancia’s father in New Jersey, “but they missed him.”

The incident also raised questions about airport security and the possible mixture of mental illness and weapons, as well as about Ciancia’s state of mind.

According to the Associated Press, Ciancia said in the note found by authorities that he wished to kill at least one Transportation Security Administration officer but did not care who.

“Black, white, yellow, brown, I don’t discriminate,” the note read, as paraphrased for AP by a law enforcement official who was briefed on the investigation but not authorized to speak publicly.

As described to AP, the note appeared to contain terms and references often found in messages from antigovernment fringe groups. One of the terms was “fiat currency,” AP said. The letters NWO also were used, in apparent reference to “New World Order,” a term used by groups claiming the existence of global conspiracies.

The federal government created the TSA to upgrade airport security after the Sept. 11, 2001, terrorist attacks. Over the years, complaints have emerged about TSA’s screening efforts, which some air travelers have described as onerous and intrusive.

Ciancia’s relatives could not be immediately reached Saturday.

But little that could be found on Saturday suggested an association between Ciancia and the antigovernment hostility said to have been expressed in the note.

Ciancia grew up in the southwestern corner of New Jersey in Pennsville, where his father owned an auto-repair shop and was known as a pillar of the local community. His mother, who had been a teacher in a Catholic school, died more than four years ago. The town’s police chief said he had never had trouble “with anyone” in the family.

A former classmate at Salesianum High School in Wilmington, Del., where Ciancia graduated in 2008, described him as “kind of quiet and timid, but smart.”

The classmate, James Kerrigan, called him “a nice guy” who “never struck me as the type that would do this sort of thing.”

Others who knew him in high school also called him quiet and shy, with no signs of violent tendencies. David Hamilton, who also graduated from Salesianum in 2008, told the Los Angeles Times that Ciancia “kept to himself and ate lunch alone a lot.”

A 17-year-old living across the street from Ciancia’s family home said, according to the Philadelphia Inquirer, that “you wouldn’t think someone like that would come out of a family like that.”

James Mincey, who said he had shared a Los Angeles apartment with Ciancia until February, told an ABC affiliate that he was shocked. “From knowing this guy, it just doesn’t make sense,” he said.

After finishing high school, Ciancia had worked for a time for his father, said New Jersey neighbor Gary Hankins. It was not clear when Ciancia moved to Los Angeles or what he was doing there. AP described him as an unemployed motorcycle mechanic.

Current roommates reportedly said he had seemed fine as recently as Thursday.

It was not clear when or where the rifle was purchased.

The airport said in a statement that 40 flights were affected Saturday, including 30 cancellations and 10 delays that slowed an estimated 4,000 passengers. On the day of the shooting, an estimated 1,550 scheduled flights and 167,000 passengers were affected, according to the statement.

Los Angeles Airport Police Chief Pat Gannon said at the Saturday news conference that the LAPD dedicated extra resources to the airport and that visitors will see an increased law-enforcement presence for some time.

Along those lines, the TSA said it would review its policy on officer safety.

TSA Administrator John Pistole said Saturday that the agency would make every effort to make certain Friday’s events are not repeated.

Marcia D. Davis in Pennsville and Rachel Weiner contributed to this report.