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Christopher Woodyard, John Bacon, and Doug Stanglin USA TODAY

LOS ANGELES ? A lone gunman armed with a semi-automatic rifle went on a shooting spree Friday at Los Angeles International Airport, killing one person and leaving at least six people injured before the suspect was tracked down and taken into custody.

"We have one deceased,'' Capt. Brian Elias of the Los Angeles County Coroner's office told USA TODAY.

Tim Kauffman, a spokesman for the American Federation of Government Employees in Washington, told the Associated Press that the victim who died was a Transportation Security Administration officer. He said the union's information came from its local officials in Los Angeles.

Airport police chief Patrick Gannon said the gunman forced his way past a TSA checkpoint into the heart of LAX Terminal 3.

He said authorities believe the gunman acted alone.

The shooter, described as a 23-year-old U.S. citizen, was shot in the face in the confrontation with police, a federal law enforcement official said. The official, who was not authorized to speak publicly, said the suspect had survived the shooting but his condition was not immediately known.

One TSA officer is the only person confirmed dead, the official said.

Gannon said the shooting began at 9:20 a.m. PT, when the suspect pulled an "assault rifle" out of a bag and began to open fire in LAX Terminal 3.

"He proceeded up to the screening area and continued shooting, and went past the screeners back to the airport itself," Gannon said.

Airport police "responded immediately," he said, tracking down the shooter and taking him into custody.

The shooting spree brought the giant airport complex to a halt, with travelers marooned on buses or sidewalks and police doing their best to unsnarl traffic.

LAPD Assistant Chief Earl Paysinger says the suspect was armed with a semi-automatic rifle.

Dana Starfield tells KCBS-TV that she heard a boom behind her while standing in the security line.

"We heard someone scream, 'A gun, everybody get down, get down.' ... We just crawled through the security gate.''

Starfield said Virgin airline employees guided her and several others into a small room, where they tried to block entry by moving a copying machine in front of the door.

"We heard a few more booms,'' she said.

She said that about 15 minutes later, SWAT officers came through and led them to safety.

Luke and Alexa Sieber of Green Bay, Wis., were in line at an airport counter when they heard eight shots, followed by another burst of 20.

Witness Brian Keech said he heard "about a dozen gunshots" from inside the security gate at Terminal 3, which serves Allegiant Air, Frontier, JetBlue, Spirit, Virgin America and other airlines.

Officials at a news conference declined to discuss injuries in detail, saying only that authorities treated seven people for injuries at the airport and that six were transported to the hospital.

Ronald Reagan UCLA Medical Center said it had received "three male victims from the LAX Airport shootings. One arrived in critical condition, and two are listed in fair condition."

Flights heading to the Los Angeles airport were held at their departure airports, according to FlightAware.com, which tracks flights.

LAPD Police Chief Charlie Beck and Los Angeles Mayor Eric Garcetti rushed to the airport as the drama unfolded.

President Obama has been briefed on the shooting, the White House says.

Contributing: Kevin Johnson in Washington, Associated Press