An Army veteran who flew from Alaska to Florida opened fire in the baggage claim at Fort Lauderdale-Hollywood International airport Friday, killing five people, injuring eight and sending terrified passengers running through the airport before police grabbed the suspect unharmed, according to law enforcement authorities.

Witnesses said the 26-year-old man - described by his aunt as behaving erratically in recent weeks and possibly having "lost his mind" - emptied several magazines of bullets, then dropped to the floor spread-eagled to await arrest. He was taken into custody without incident by a Broward County sheriff's deputy, according to Sheriff Scott Israel.

“People started kind of screaming and trying to get out of any door they could or hide under the chairs,” a witness, Mark Lea, told MSNBC. “He just kind of continued coming in, just randomly shooting at people, no rhyme or reason to it . . . He wasn't targeting anyone."

Chip LaMarca, a Broward County commissioner, was briefed on the airport shooting by the Broward Sheriff’s office. On his Twitter account, he said the shooter arrived in Fort Lauderdale aboard a flight with a gun in a checked bag.

"He claimed his bag and took the gun from baggage and went into the bathroom to load it. Came out shooting people in baggage claim," LaMarca tweeted.

A federal law enforcement official, who is not authorized to comment publicly on the case, identified the suspect as Esteban Santiago. Sen. Bill Nelson, a Florida Democrat, said earlier that the gunman was carrying a military ID in that name.

Santiago arrived in Fort Lauderdale early Friday aboard a Delta flight that originated Thursday in Anchorage and passed through Minneapolis, the federal official said.

The official said the suspect apparently retrieved a handgun from his checked luggage and loaded it before launching an indiscriminate assault.

In November, the suspect appeared unannounced in the FBI offices in Anchorage, complaining that the Islamic State had gained control of his mind and the terror group was urging him to fight on its behalf, the official said.

The FBI conducted a background check, learning of his military record, which included service in Iraq, but found no connection to terror groups. Determining that the man apparently needed psychiatric care, the FBI alerted local law enforcement and turned him over to their custody for a medical referral. It is not clear whether Santiago received treatment following that incident.

The official said Santiago worked in Anchorage in a security-related job and has a girlfriend and a child there.

Santiago's aunt, Maria Ruiz, who lives in Union City, N.J., said her nephew is an Army veteran who served two years in Iraq and came back acting strangely. However, she said that he “was happy with the kid” after the birth of his child last year.

“I don’t know why this happened,” she said during an interview at her home Friday afternoon.

She said that her nephew had been living in Alaska, where he was able to obtain the security job. She showed reporters a photo of Santiago at a hospital holding his newborn son in September. Staff at Providence Hospital in Anchorage confirmed that the photo was taken in their hospital.

In the photo, Santiago wore a T-shirt emblazoned with the word "Disturbed," an apparent reference to the heavy metal band of the same name. Ruiz said that Santiago, whose mother lives in Puerto Rico, seemed to be happy - but shortly thereafter, he seemed to come unglued, she said.

“Like a month ago, it was like he lost his mind,” she said. “He said he saw things.”

She said that he was hospitalized for two weeks, but she did not have details about his condition.

Ruiz spoke to reporters at her home Friday afternoon before FBI agents showed up at her door and local authorities closed off the street near her home.

Sheriff Israel said authorities had not established a motive for the shooting and that it was too early to declare it a terrorist act.

"At this point, it looks like he acted alone," Israel told reporters. He called the shootings a "horrific, horrific act."

President-elect Donald Trump urged tweeted that he was following the events. "Monitoring the terrible situation in Florida," Trump wrote on Twitter. "Just spoke to Governor [Rick] Scott. Thoughts and prayers for all. Stay safe!"

The melee, which erupted around 1 p.m. EST, brought air traffic to a standstill at the heavily traveled airport. Some incoming flights were halted on the tarmac and were likely to be sent to another city without allowing passengers to disembark, according to airport director Mark Gale.

The shooter, described as slender, about 5-foot-7 and wearing a blue T-shirt, did not say a word during the incident, calmly opening fire as he strolled among passengers at a baggage carousel in Terminal 2, which services Delta flights.

It is legal for airline passengers to travel with guns and ammunition as long as the firearms are put in a checked bag — not a carry-on — and are unloaded and locked in a hard-sided container. Guns must be declared to the airline at check-in.

Santiago arrived in Fort Lauderdale after having checked only one piece of luggage — his gun, said Jesse Davis, police chief at the Anchorage airport.

Another witness, John Schicher, told MSNBC the shooter appeared to be wearing a blue Star Wars T-shirt.

The shooting sent people scrambling onto the tarmac, some carrying luggage. Others cowered behind cars.

Video posted on Instagram appeared to show several people wounded in the baggage claim area of the terminal. One person appeared to be lying in a pool of blood with a head wound.

Paramedics could also be seen treating a bleeding victim outside the airport. Hundreds of people stood on the tarmac as an ambulance drove by.

Florida Gov. Rick Scott called the shooting a "senseless act of evil" and added that he called Trump to keep him informed about the case.

Early word on the incident came from a tweet by Ari Fleischer, former White House spokesman for President George W. Bush. "I'm at the Ft. Lauderdale Airport," Fleischer tweeted. "Shots have been fired. Everyone is running."

Contributing: Kevin Johnson, in Washington; Abbott Koloff and Monsy Alvarado, The (Bergen County, N.J.) Record ; the Associated Press