A gunman believed to be an Iraq war veteran opened fire at Fort Lauderdale's international airport, killing five people and wounding eight before being taken into custody, officials and witnesses said.
The shooting spree sent panicked travellers running for cover inside the terminal and on the runway apron, with dozens of people corralled into large groups on the tarmac. Aviation authorities shut down air traffic, stranding hundreds of travellers.
The shooter was identified as Esteban Santiago, 26, and was carrying US military identification, according to a spokesman for Senator Bill Nelson of Florida, who spoke with officials at the Transportation Security Administration (TSA).
Mr Santiago served from 2007 to 2016 in the Puerto Rico National Guard and Alaska National Guard including a deployment to Iraq from 2010 to 2011, according to the Pentagon.
A private first class and combat engineer, he received half a dozen medals before being transferred to the inactive ready reserve in August last year.
The gunman had arrived on a flight to Fort Lauderdale with a checked gun in his bag, and upon claiming the luggage went to the bathroom to load the gun, Broward County Commissioner Chip LaMarca said on Twitter. He came out firing, Mr LaMarca said, and witnesses told MSNBC television he only stopped upon running out of ammunition, at which point he surrendered to police.
Cellphone video posted on social media showed victims on the floor next to a carousel, with people on their knees attempting to provide aid. At least two victims had pools of blood from apparent head wounds.
John Schlicher, who told MSNBC he saw the attack, described the shooter as a "slender man" who was "directly firing at us" while passengers waited for their bags to come off the carousel.
"I put my head down and prayed," Mr Schlicher said, adding that his wife gave first aid to someone who had been shot in the head.
His mother-in-law used her sweater to tend to another victim but it turned out that victim was already dead, Mr Schlicher said.
Mark Lea, another eyewitness, told MSNBC "there was no rhyme or reason to it."
"He didn't say anything, he was quiet the whole time, he didn't yell anything," Lea said.
Flying with firearms is routine and legal in the United States as long as the guns are kept in a locked, hard-sided container as checked baggage only, under TSA rules. Ammunition is prohibited in carry-on bags but is allowed in checked luggage.
The shooter was unharmed as law enforcement officers never fired a shot, Broward County Sheriff Scott Israel told reporters at the airport, adding it was too early to assign a motive.
"At this point, it looks like he acted alone," Israel said while police continued to search the airport.
The shooter, who wore a "Star Wars" T-shirt, said nothing as he fired, witnesses told MSNBC. He appeared to use a 9mm handgun, which he tossed aside upon firing all his rounds, MSNBC reported.
"This is a senseless act of evil," Florida Governor Rick Scott told reporters.
The attack was the latest in a series of mass shootings that have plagued the United States in recent years, some inspired by militants with an extreme view of Islam, others carried out by loners or the mentally disturbed who have easy access to weapons under US gun laws.
Fort Lauderdale-Hollywood International Airport is the second largest in South Florida, serving as an intercontinental gateway, with Miami International Airport known as the primary airport for international flights in the area.
Attention was likely to focus on impact of his service in the Iraq war. An aunt said he came back from the war "a different person" after his deployment, MSNBC reported.
Today's attack comes nearly two months after a former Southwest Airlines worker killed an employee of the company at Oklahoma City's airport, in what police called a premeditated act.
The deadliest mass shooting in modern US history took place in June, when a gunman apparently inspired by Islamic State killed 53 people and wounded 49 others at a gay nightclub in Orlando, Florida.
One of the most shocking took place in 2012, when a man entered an elementary school in Newtown, Connecticut, and shot dead 20 first-graders and six adults.
Attackers from Fort Lauderdale to Brussels have exploited security officials' focus on preventing attacks on airplanes rather than inside airports. In Western Europe and the United States, terminals are easily accessible public spaces.
But at Israel's Ben Gurion Airport, widely seen as a model for security, private companies trained by the national security agency use bomb-detectors, profile passengers and question travellers under the watch of police at the airport's entrance. That approach has its limitations and may just shift the target to another location at the airport, experts have said.