Airport officials sort a large pile of luggage inside Terminal 3 outside the area where a shooting incident occurred the previous day at Los Angeles airport (LAX), California November 2, 2013. [Photo/Agencies]

US Rep. Michael McCaul, 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.

Authorities believe the rifle used in the shooting was purchased in Los Angeles. Ciancia also had two additional handguns that he purchased in Los Angeles, but which weren't at the crime scene, a law enforcement official said. The official, who has been briefed on the investigation, was not authorized to speak publicly and requested anonymity.

The purchases themselves appeared legal, although authorities were still tracing them, and it's unclear if the shooter used his own identification or someone else's, the official said.

"He didn't buy them on the street. He didn't buy them on the Internet," the official said. "He bought them from a licensed gun dealer - the rifle and the two handguns."

Hernandez, a three-year veteran of the TSA, moved to the US from El Salvador at age 15, married his sweetheart, Ana, on Valentine's Day in 1998 and had two children.

The other two TSA officers wounded in the attack have been released from the hospital.

Brian Ludmer, a Calabasas High School teacher, remained in fair condition at Ronald Regan UCLA Medical Center with a gunshot wound to the leg.

His family declined to comment and asked for privacy, hospital officials said.

The FBI was still looking into Ciancia's past, but investigators said they had not found evidence of previous crimes or any run-ins with the TSA. They said he had never applied for a job with the agency.