An Iraq war veteran took a gun out of his checked luggage and opened fire in a crowded baggage claim area at Fort Lauderdale's airport on Friday, killing five people, months after he showed up at an FBI office behaving erratically.
Esteban Santiago, 26, who was taken into custody immediately following the shooting and questioned at length, was expected to face federal charges in the shooting rampage, said George Piro, special agent in charge of the Federal Bureau of Investigation's office in Miami.
Piro said investigators had not ruled out terrorism as a possible motive in the rampage and were reviewing the suspect's recent travel.
Santiago, who had served in the U.S. military, had arrived in Ft. Lauderdale shortly before 1pm local time (1800 GMT) on a connecting flight from Alaska, authorities said, when he retrieved a 9mm semi-automatic handgun from his checked luggage and began firing indiscriminately.
Broward County Commissioner Chip LaMarca said on Twitter that the gunman went into a restroom to load his weapon and came out firing. Witnesses told MSNBC television he only stopped after running out of ammunition, at which point he surrendered to police.
Cellphone video posted on social media showed travellers kneeling and treating victims on the floor next to a carousel. At least two victims had pools of blood from apparent head wounds.
The gunman, who wore a "Star Wars" T-shirt, said nothing as he fired, witnesses told MSNBC.
"This is a senseless act of evil," Florida Governor Rick Scott told reporters.
A White House spokesman said President Barack Obama had spoken to Scott and Broward County Mayor Barbara Sharief and had extended his condolences to the loved ones of the victims.
In addition to the five killed, eight others were wounded by gunfire and some three dozen were taken to local hospitals with bruises or broken bones suffered in the chaos surrounding the shooting massacre.
Piro said that Santiago had turned up at an FBI office in Anchorage in November of last year behaving erratically and was turned over to local police, who took him to a medical facility for a mental evaluation.
A federal law enforcement official told Reuters that Santiago told agents at the Anchorage office in November that his mind was being controlled by a U.S. intelligence agency, which was ordering him to watch Islamic State videos.
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.
An aunt said he came back from his deployment "a different person," MSNBC reported.
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 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.
John Schlicher, who told MSNBC he saw the attack, said the shooter was "directly firing at us" while passengers waited for their bags. His wife gave first aid to a victim who had been shot in the head, and his mother-in-law used her sweater to tend to another victim but it turned out that person was already dead, he said.
Mark Lea, another eyewitness, told MSNBC, "He didn't say anything; he was quiet the whole time."
Fort Lauderdale-Hollywood International Airport is the second largest in South Florida, serving as an intercontinental gateway.
Nearly two months ago 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 last June, when a gunman apparently inspired by Islamic State killed 49 people and wounded 53 at a gay nightclub in Orlando, Florida.
