It was a chaotic and scary scene for passengers traveling through LAX’s Terminal 3 Friday morning when a gunman opened fire, injuring seven and killing an officer of the federal Transportation Security Administration before breaching security and making his way nearly to airline gates before being taken down in an exchange of gunfire with airport police.

FBI complaint | Timeline of shooting

Update 4:34 p.m. Suspect Paul Ciancia could face death penalty in LAX shooting

The official complaint by the federal government against suspected LAX shooter Paul Anthony Ciancia was filed Saturday in U.S. District Court in California. Ciancia faces two potential maximum sentences: the death penalty or life without the possibility of parole, officials said at a Saturday press conference, depending on what the attorney general decides.

Speaking at the Federal Building in Westwood, U.S. Attorney Andre Birotte Jr. said the murder charge applied to the death of TSA officer Gerardo Hernandez, who died in Friday's shooting at LAX's Terminal 3.

Ciancia remained unresponsive Saturday afternoon and authorities have been unable to interview him, FBI special agent David Bowdich said. The suspect is believed to be in critical condition at the Ronald Reagan UCLA Medical Center in Westwood.

"We believe he was dropped off" at the airport, Bowdich told reporters at the press conference, but declined to comment on who drove Ciancia to LAX. Bowdich said there is video evidence of the incident, but authorities don't know where Ciancia allegedly entered the airport.

Bowdich said authorities are still building a profile of Ciancia. FBI special agent Stephen Khoobyarian writes in the complaint that other agents told him that a handwritten letter allegedly signed by Ciancia was recovered from his bag.

"In that note, he indicated his anger and his malice toward the TSA officers," Bowdich said.

The letter stated he'd "made the conscious decision to try to kill" multiple TSA employees. The letter allegedly said that Ciancia wanted to "instill fear in your traitorous minds."

Addressing questions as to why Ciancia targeted TSA agents, Bowdich said the suspect had never applied for a job with the agency and had no known run-ins with the TSA or law enforcement.

Contrary to earlier reports, Ciancia was not a ticketed passenger, Bowdich said.

The complaint charges Ciancia with allegedly killing and attempting to kill TSA officers. The TSA is part of the federal government's executive branch.

Ciancia allegedly pulled a Smith & Wesson .223 caliber M&P-15 assault rifle from his bag, according to the complaint, before confronting TSA agent Hernandez inside Terminal 3 at the street-level pre-screening area. Ciancia allegedly fired multiple shots at point-blank range at Hernandez.

"Ciancia began to walk up an escalator, looked back at the wounded officer, who in video appeared to move, and returned to shoot the wounded officer again," the complaint reads. That left the officer fatally wounded, according to the complaint.

Ciancia allegedly shot two other TSA employees and one civilian passenger, according to the complaint.

Ciancia was then shot by an L.A. World Airport Police sergeant and an officer, according to the complaint.

Bowdich said that there were five gunshot victims, including the TSA agent who was killed.

Ciancia allegedly fired "a significant number" of rounds, Bowdich said. Ciancia also had five magazine clips of assault rifle ammunition with him, according to the complaint.

Officials are still reviewing surveillance video, Bowdich said.

Read the full complaint below:

Ciancia complaint

— Mike Roe

Update 3:13 p.m. TSA to review security after shooting

The Associated Press reports that the Transportation Security Administration will review its policy on officer safety in the wake of the deadly shooting at Los Angeles International Airport.

According to the AP:

TSA Administrator John Pistole said Saturday that the agency's officers are "the first line of defense" in airport security. He said the agency would do everything possible to make sure Friday's tragedy was never repeated. Pistole did not say if that meant arming officers. He spoke outside the home of slain TSA officer Gerardo Hernandez.

Yesterday, L.A. Airport Police Union President Marshall McClain told KPCC that the suspected shooter Anthony Ciancia entered through the exit door before opening fire on TSA officials.

— KPCC & wires

Update 2:28 p.m. New Jersey community that suspect called home shocked by his actions

The community of Pennsville, New Jersey, where the suspected shooter is from, is shocked by Paul Anthony Ciancia's actions while sympathizing with his family.

(This photo provided by the FBI shows Paul Ciancia, 23.)

Delaware's News Journal reports Ciancia graduated from Salesianum School, a private Catholic school in Wilmington, Delaware that has a large number of graduates in law enforcement.

The News Journal quotes several residents who say there wasn't anything particularly noticable about Ciancia:

“There was something obviously wrong with him,” said [13-year Pennsville resident Dawn] Troupe, who also said she doesn’t know the Ciancias. “He was calling out for help to somebody. If he survives, hopefully he’ll get the help that he needs.

Another resident told the paper that residents are rallying around their family and the Pennsville community, as well as trying to understand what could have driven Ciancia to commit such an action:

“In the hometown here, everyone’s sympathizing with the shooter,” said Nancy Sherman, of Pennsville, who added that she does not know the family. “And I get a little annoyed with that, because very little is said about the victim who was killed and his family. And I get a little sad about that. But there’s a lot of sympathy in this town for the shooter.”

— KPCC staff

Update 2:12 p.m. TSA agent killed by shooter Saturday mourned

The family of the TSA agent killed at LAX Saturday, Gerardo Hernandez, were mourning his loss Saturday.

(TSA agent Gerardo Hernandez, killed Friday, Nov. 1, 2013 in a shooting at LAX. Photo courtesy Courtesy NBC4)

“He was in front of the counter checking passports,” Hernandez's sister-in-law Xiumara Hernandez told the San Gabriel Valley Tribune.

She said that rescuers weren't able to help her brother-in-law right away, the Tribune reports. She said that paramedics rushed him into surgery, but he was pronounced dead at 11 a.m.

Hernandez migrated to L.A. from El Salvador at 16, Hernandez's brother Francisco told the Tribune.

Read more at the San Gabriel Valley Tribune.

— KPCC staff

Update 1:38 p.m. Terminal 3 reopens at LAX

Terminal 3 reopened Saturday afternoon at LAX following a shooting Friday that killed TSA agent Gerardo Hernandez. The announcement was made by L.A. World Airports Executive Director Gina Marie Lindsey during an afternoon press conference.

"Our security profile is high profile," Los Angeles Airport Chief Patrick Gannon said. They were putting that high profile out at curbs, ticketing areas and elsewhere on their airport campuses, Gannon said.

Gannon also defended his decision to reassign officers from security checkpoints to in front of the checkpoints. He added that the FBI to him that his officers were 60 seconds behind the suspect.

"If I was a football coach and played the same play every time, I wouldn't gain a yard," Gannon said. He said the same held true with security. "I made a decision over the last year to move those individuals from behind security to out in front and gave them greater responsibility."

Officers were chasing the suspect through the terminal within seconds, Gannon said.

Gannon said he wanted to emphasize that after the TSA officer was shot, while some went after the suspect, others treated the wounded officer using portable trauma kits. He added that they then put him in a wheelchair and took him to an ambulance.

Gannon said that officers who confronted the shooter are doing well, though it was still a traumatic incident for them. They spoke with investigators into the wee hours about the case, Gannon said.

LAPD and federal air marshals have committed additional resources to the airport following Friday's shooting, Gannon said. Other agencies in the area have offered resources if needed, according to Gannon.

Gannon said that L.A. Airport Police completed an exercise at an old terminal in Ontario last month, practicing for a similar event. He drew a comparison between what happened at the airport to recent attacks in Nairobi, the Washington D.C. Navy Yard and at Sandy Hook Elementary. Over 200 Airport Police participated in the training, Gannon said, along with about 200 from LAPD.

— Ed Joyce & Mike Roe

Update 10:32 a.m. What we know about suspected shooter Paul Anthony Ciancia

The suspected gunmen, Paul Ciancia, moved to Los Angeles about a year ago from his hometown in New Jersey. At one point he rented a couch in an apartment near Los Feliz. (The hall at the apartment complex where Paul Anthony Ciancia lived in Los Feliz, Calif. Photo: Mae Ryan/ KPCC) KNBC aired an interview with Ciancia's former roommate, James Mincey, earlier. Among other things, Mincey said that Ciancia was introverted and didn't seem at all violent, and said he was "taking a break" in California. When the two met up for lunch a week ago, Ciancia told Mincey he was heading back to New Jersey. Watch the interview here. Moments after gunfire broke out at the Los Angeles airport, Paul Ciancia's father called police in New Jersey, worried about his son in L.A., the Associated Press reports, citing Pennsville, New Jersey police chief Allen Cummings. The young man had sent texts to his family that suggested he might be in trouble, at one point even saying goodbye. The call came too late. According to the AP, 10 minutes earlier, police said, the 23-year-old had walked into LAX, pulled an assault rifle from his bag and began firing at Transportation Security Administration officers. Pennsville is a small blue-collar town near the Delaware River where Ciancia grew up. AP reports that Cummings said he's known Ciancia's father — also named Paul — for more than 20 years. He said the father called him around 12:30 p.m. EDT/9:30 a.m. PDT Friday to tell him about texts his family had received from his son in Los Angeles. "There was some things in there that made his family feel he may do harm to himself," Cummings said, according to AP. He did not mention suicide or hurting others, but he did say goodbye. Cummings said the father also heard from a friend that his son may have had a gun. The chief said he called Los Angeles police, who sent a patrol car to Ciancia's apartment. Cummings said he never met Paul Ciancia Jr., according to AP, but that he learned from his father that he attended a technical school in Florida, then moved to Los Angeles in 2012 hoping to get a job as a motorcycle mechanic. But he was having trouble finding work. "I've never dealt with the kids," the chief said, according to AP. "They were never on the police blotter, nothing like that." AP reports that Leon Saryan had just passed through security and was looking for a place to put his shoes and belt back on when he heard gunshots. He fled with a TSA worker, who he said was later wounded slightly, and managed to hide in a store. As he was cowering in the corner, the shooter approached. "He looked at me and asked, 'TSA?' I shook my head no, and he continued on down toward the gate. He had his gun at the ready and, but for the grace of God, I am here to tell about it," said Saryan, of Milwaukee, AP reports. Update 7 a.m. Chaos, fear as gunman stalked Terminal 3

The FBI, which is taking the lead in investigating the shooting, identified the suspect as 23-year-old Paul Anthony Ciancia.

The airport was bustling Saturday morning as usual, except for Terminal 3. That terminal is scheduled to remain closed until the FBI's investigation is complete, according to the airport's official Twitter account.

"It was a day yesterday, we won't forget it," said Dave Henry. His wife Lisa said she saw muzzle flashes.

LAX initially announced that those who left their belongings when fleeing the terminal would be able to claim them, but that announcement was reversed, with passengers told they wouldn't be able to retrieve their possessions until the FBI's investigation of the scene was complete. (Officials have since said passengers can pick up their luggage at their respective airliner's terminal beginning at 10 a.m. Saturday. Read more)

The airlines in Terminal 3, including Virgin America, Frontier, JetBlue, Allegiant Air and Spirit are attempting to make arrangements for the use of other LAX terminals or other local airports. The airlines expect delays and/or cancellations, and travelers were advised to call ahead before leaving for the airport. The terminal's ticket counter was open Saturday morning.

From the beginning of the incident until midnight Friday, 826 scheduled departures were impacted, as well as 724 scheduled arrivals, impacting a total of 167,050 passengers.

The TSA identified the slain officer — the first killed in the line of duty since the TSA was created in the wake of 9/11 — as Gerardo I. Hernandez, 39, of Porter Ranch.

Mayor Eric Garcetti, speaking in a press briefing Friday evening, said that Ciancia was a Los Angeles resident; he was reportedly from Pennsville, New Jersey.

Garcetti said the shooting could have been much, much worse. “There [were] additional rounds that this suspect had, and the fact that these officers were able to neutralize the threat as they did was amazing," Garcetti said. "He could have literally killed everyone in the terminal.”

RELATED: LAX shooting: Suspect ID'd, TSA officer dead, 7 injured in Terminal 3 (updates)

The incident began at about 9:20 a.m., when a gunman walked into Terminal 3, grabbed an assault rifle from his bag and started firing, police told reporters.

Milton Pool was standing in line, waiting to check in for his flight to Little Rock, when the shooting took place. “I heard two shots," he told KPCC's Ben Bergman. "I started running, and then about five seconds later I heard about 10 shots.”

People in the terminal hid in closets or behind ticket counters. Pool said that he decided to run. “Everybody was hiding under chairs or lying down," he said. "But I knew from recent incidents they follow people, so I just started running out of the building.”

Orange County resident Jose Mares told KPCC that he was on his way to Oklahoma City with his wife when he heard a loud bang. “We thought it was just something that fell down," he said. "But it was louder than that. That’s when the second one when off, multiple shots."

Mares said the shooter ran up the escalator, towards the TSA checkpoint and started firing at those below with two guns. “He was wearing all blue. He looked like a TSA guy ... like one of them. He blended in pretty good. He had a baseball cap on.”

(Law enforcement officials have said nothing that would corroborate Mares' account; in particular, they have said nothing specific about the shooter's weapons, other than that he was armed with an assault rifle, nor his attire. The TSA has said the suspect in the case, Ciancia, is not affiliated with the TSA.)

(Update, Nov. 4: Much of what this witness told the media has been discredited.)

Panic, and a scramble for cover

For his part, Mares said that he worried that if he made a run for it, he might attract the shooter’s attention and that he might get shot. So he threw his wife on the ground and hid.

“I just threw a bunch of luggage on her just for her protection, and I was just keeping an eye on the shooter, so once he was shooting at us, that’s when we had our chance to leave,” he said.

Mares escaped unscathed.

Meanwhile, the gunman made it through the TSA checkpoint, where agents are unarmed.

He killed a TSA employee, whom the TSA has identified as Hernandez, a TSA officer who was recently transferred to LAX from Montana. The slain man is the first TSA employee killed in the line of duty.

Once inside the main terminal, according to witnesses, the gunman calmly walked down a long hallway past the restrooms, past a Jetblue gate, a newsstand and a duty-free shop, and ended up next to a Burger King near the circular waiting area and gates from which most of the terminal's flights take off.

Patrick Gannon, the police chief for Los Angeles World Airports, said that response was swift. “Personnel officers from L.A. Airport police responded immediately to calls and tracked the individual through the airport and engaged him in gunfire in Terminal 3,” he said in the Friday afternoon press briefing.

On Friday, Ciancia's father in New Jersey had called authorities for help in finding his son after the young man sent one of his siblings a text message about committing suicide, Pennsville Police Chief Allen Cummings said, the Associated Press reports.

The chief said he called Los Angeles police, who sent a patrol car to Ciancia's apartment. There, two roommates said that they had seen him a day earlier and he had appeared to be fine.

Cummings said that the Ciancias — owners of an auto body shop — are a "good family" and that his department had had no dealings with the son.

Aside from the one TSA employee killed and another injured, everyone else was hurt as they were running away.

"No words can explain the horror that we experienced today," TSA Administrator John Pistole said in a message to employees Friday.

Pistole said he planned to arrive in Los Angeles on Saturday to meet with Hernandez's family and the injured employees.

It was not the first shooting at LAX. On July 4, 2002, a limousine driver opened fire at the airport's El Al ticket counter, killing an airline employee and a person who was dropping off a friend at the terminal. Police killed the man.

President Barack Obama called the head of the Transportation Security Administration to express his condolences to the families and friends of the dead and injured TSA officers.

Why the gunman only seemed to target TSA employees isn’t known yet, just like so many other details that remain a mystery.

RELATED: Timeline of the shooting at LAX

— Ben Bergman with AP

An earlier version of this story incorrectly stated what kind of TSA agent Hernandez was.

This story has been updated.