When Congress formed the Transportation Security Administration two months after 9/11, the agency's mission was clear: Its officers would not carry guns or make arrests. Instead, they would focus on screening passengers for weapons, bombs and other dangerous materials.

But the shooting death of a TSA officer at Los Angeles International Airport — the first fatality in the agency's history — could change that.

On Monday, the union representing 45,000 federal security agents called for the creation of a class of armed TSA officers with law enforcement training and the authority to arrest people.

"The sad truth is that our TSA officers are subject to daily verbal assaults and far too frequent physical attacks," said Jeffrey David Cox Sr., president of the American Federation of Government Employees. "We feel a larger and more consistent armed presence in screening areas would be a positive step."

TSA Administrator John Pistole said his agency would review its protocols after Friday's attack.

U.S. Atty. Gen. Eric Holder also weighed in Monday, saying that the government should examine the agency's role in protecting airports.

Part of the investigation will be "a review of the security measures that were in place not only at LAX but, I think, a review of the security arrangements that exist in other airports as well," he said.

TSA Agent Gerardo I. Hernandez was killed and at least three other people were wounded Friday morning when a gunman identified by police as 23-year-old Paul Anthony Ciancia opened fire at the entrance to a security checkpoint, sending travelers scrambling for cover and grounding flights for hours. Ciancia, who authorities say targeted TSA officers and left an anti-government suicide note, continued his rampage up an escalator and down a long corridor deep into Terminal 3 before being shot by airport police.

In a search warrant affidavit for Ciancia's cellphone, FBI officials said Ciancia's roommate dropped him off at the Virgin Airlines terminal Friday morning after Ciancia "entered his room unannounced and asked to be driven to LAX." The roommate didn't learn about the shooting until he returned to his apartment, according to the warrant, which was signed Monday.

Ciancia's family said through an attorney that they were cooperating fully with the FBI and other law enforcement agencies.

"We, like most Americans, are shocked and numbed by the tragic events," the family said.

Ciancia's family notified Los Angeles police Friday morning after receiving text messages from the 23-year-old that made them concerned about his well-being, a New Jersey police chief and friend of Ciancia's father said. But by the time officers arrived at the apartment, he was gone.

When Ciancia arrived at the screening checkpoint at Terminal 3, there were no armed officers. Some have questioned whether the incident would have ended more quickly if there had been.

But security experts warn that arming TSA officers would be an extremely expensive undertaking that could divert agents from their primary task of screening passengers for dangerous items.

"I want those guys focused on looking at my bag and looking at people," said Jeff Price, an aviation security expert who teaches at Metropolitan State University of Denver.

He said arming TSA screeners would be an "overkill" solution that could cost billions of dollars and would require officers to undergo considerable training. "There are other ways that you can provide the level of protection that the TSA screeners deserve without giving them all guns," he said.

Brian Jenkins, an authority on terrorism and aviation security at the Santa Monica-based Rand Corp., said that arming TSA screeners would dramatically change the public's perception of them.

TSA officers are already viewed by some as symbols of government overreach.

With 800 million air passengers each year, that would create "800 million direct encounters between the American public and armed federal authorities," Jenkins said.

"Heaven forbid we end up in a situation where in the course of a gunfight at a checkpoint, civilians were killed by friendly fire," he said. "This would be a catastrophe for the TSA."