(NBC) -- A man pulled an assault rifle from a bag and shot his way through security at Los Angeles International Airport on Friday, killing one Transportation Security Administration worker, wounding as many as three others and sending terrified travelers diving for cover and fleeing onto the tarmac, authorities and witnesses said.
The gunman was shot by law enforcement and taken into custody.
The shooting started at about 9:20 a.m. local time at Terminal 3. The gunman took out the rifle and opened fire at the security checkpoint, then went far into the terminal, where he was captured after exchanging fire with law enforcement, authorities said.
When the gunfire erupted, travelers who were waiting to snake through the security line suddenly had to abandon their suitcases and hit the ground.
The shooting brought one of the nation's busiest airports to a standstill. The Federal Aviation Administration grounded flights at LAX, where 1,500 flights take off and land every day. Passengers heading there for departing flights were stuck in colossal traffic jams. Some abandoned their rides and rolled their suitcases the last distance to the airport.
Federal officials, citing initial information, told NBC News that the suspect was a U.S. citizen in his early 20s. A witness, Leon Saryan, told MSNBC that he was cowering in a corner when the gunman approached him and asked: "TSA?" Saryan said he was wearing street clothes, and "he could see I didn't have a uniform."
"He was calm. He was walking slowly," Saryan said. "He must have felt that he was in control, because he had his weapon and nobody else did at that time."
"But for the grace of God I would have been one of the fatalities," he said.
The airport said that seven people were injured in all, but the nature of the injuries was not clear. UCLA Medical Center said it had one patient in critical condition and two in fair condition. One of the TSA workers was shot in the leg, said Nico Melendez, a spokesman for the Transportation Security Administration.
Brian Adamick, an accountant who was waiting for a flight to Chicago, said he saw a bunch of people running and one of them shouted, "There's shooting!"
He said he boarded an evacuation bus minutes later and saw a TSA agent get on, limping.
"His right ankle is injured and he gets on and sits in the seat next to me, and I said, ‘Are you OK?' He said, ‘I'm fine. I got shot. Don't worry, I've been shot before,'" Adamick told NBC News in a telephone interview.
"I said, let me take a look, and he pulls up the pant leg and there's a flesh wound — 3 to 4 inches — looks like it's straight out of Hollywood, maybe a drop of blood or two," he said.
Federal officials told NBC News that it was unclear whether the gunman was targeting the TSA or was trying to shoot his way through to get further into the airport. The gunman was in critical condition, officials said.
Terminal 3 serves Virgin America, among other airlines.
Another witness told MSNBC that there was an initial round of shots, then a pause, then more shots. An airline worker told them, "Go out! Go out!" the witness said. People streamed down the stairs and onto the tarmac for safety, he said.
President Barack Obama was briefed on the shooting, the White House said in a statement.
In 2002, an Egyptian national opened fire at the El Al ticket counter at LAX, killing two Israelis before he was shot dead. Authorities ruled it a terrorist incident, even though the shooter was not tied to a known group.