A worker drives past bags left on the tarmac at Fort Lauderdale International Airport after a gun attack that killed five people. The airport shut down for 16 hours after the incident. — Reuters

A US veteran of the Iraq war accused of shooting five people dead and wounding six others at a Florida airport has been charged with federal crimes that could carry the death penalty.

Esteban Santiago, 26, is charged with firearms offenses and carrying out an act of violence when he opened fire at the busy Fort Lauderdale airport.

Santiago, who had earlier shown signs of “erratic behavior,” arrived on a flight from Alaska on Friday.

At baggage claim he retrieved a 9mm semi-automatic handgun and ammunition that he had declared and stowed inside his checked luggage, then allegedly loaded the weapon in a bathroom and opened fire in the crowded baggage claim area of Terminal 2.

Once his ammunition was exhausted Santiago lay on the floor with his arms and legs spread out and peacefully surrendered when a sheriff deputy approached him, witnesses quoted in US media said.

The hail of bullets sent thousands scrambling for safety and shut down the airport, a major gateway to the Caribbean and Latin America.

If convicted, Santiago could face the death penalty or life in prison, US Attorney Wifredo Ferrer said in a statement.

“Santiago started shooting, aiming at his victims’ heads until he was out of ammunition,” Ferrer said.

FBI special agent George Piro said agents were looking into the motives for the attack, including “continuing to look at the terrorism angle.”

Piro said Santiago appeared to be acting alone and “every indication” is he followed rules in flying with the weapon.

Santiago is due to appear in court today.

A former member of the Puerto Rico and Alaska National Guard, he served in Iraq from April 2010 to February 2011. His military service ended in August.

On November 7, Santiago walked into the FBI office in Anchorage, Alaska and complained that his mind was being controlled by national intelligence agencies, which were forcing him to watch Islamic State jihadist videos.

This “erratic behavior” led agents to contact local police, who took him for a mental health evaluation, Piro said.

Anchorage police chief Christopher Tolley said Santiago came to the FBI office with a loaded magazine, but left his gun and newborn child in his car.

Police took the weapon for safekeeping, but he was able to reclaim it on December 8.

Santiago’s brother Bryan criticized the way authorities had handled his case.

“They had him hospitalized for four days and they let him go. How are you going to let someone leave a psychological center after four days when he said he hears voices that the CIA is telling him to join certain groups?”

The shooting renewed anxieties about airport security.

The Transportation Security Administration lets passengers travel with unloaded firearms and ammunition as checked baggage.

Congresswoman Debbie Wasserman Schultz, who represents the district that includes the airport, said the rules needed to be re-examined. The incident should prompt a review of “whether or not you should be allowed to check a firearm at all,” she said.