Alan Gomez

USA TODAY

Esteban Santiago, the 26-year-old Army veteran accused of killing five people at Fort Lauderdale-Hollywood International Airport, made his first appearance in federal court on Monday.

Little is known about why Santiago chose an airport 4,000 miles away from his hometown in Anchorage, Alaska, or what led him to unload two magazines from his Walther 9mm semiautomatic handgun at random passengers in the baggage area of the airport.

Santiago spoke with officials from the FBI and the Broward County Sheriff's Office for several hours after Friday's shooting, but the criminal complaint filed by the FBI following that interview said only that Santiago "planned the attack" without giving any indication about his motive. Those answers could become clearer through hearings in federal court, where he could face the death penalty.

Here is what we know about Santiago so far.

Troubles at home

Santiago was born in New Jersey in 1990 and moved to Puerto Rico two years later. He spent his childhood there, went to high school and joined the Puerto Rico National Guard. According to his family, things started changing for Santiago after a nine-month tour of Iraq.

"When he came back from Iraq, he was a different person," Hernan Rivera, 70, Santiago’s uncle, told The New York Times.

Santiago then moved to Alaska where he repeatedly confronted law enforcement. From January to October of 2016, he encountered Anchorage Police at least five times.

He was arrested and charged with criminal mischief following a "physical disturbance" with his girlfriend in January and was re-arrested for violating an order to stay away from their apartment the next month. But he was not arrested following three other calls. Police said each time that they could not establish probable cause.

Mental health problems

Santiago's erratic behavior escalated in November when he walked into the FBI office in Anchorage complaining that "his mind was being controlled by a U.S. intelligence agency."

FBI officials confiscated the gun he had in his car and sent him to local police, who sent him to get a mental health evaluation. He was cleared, and the FBI closed its file on him and returned his handgun.

But even neighbors sensed that something was changing with Santiago. Many Alaskans already suffer from seasonal affective disorders due to the limited sunlight that reaches the northern state.

"Or it could be (post-traumatic stress disorder) combined with alcohol," Anchorage neighbor Brittany Adams said. "We see way too much of that up here."

Shooting spree

Just before 1 p.m. on Friday, the FBI says Santiago retrieved his checked baggage at the Fort Lauderdale airport after flying from Alaska with a connection in Minneapolis.

He then went into a bathroom and loaded his gun inside a bathroom stall. George Piro, special agent in charge of the FBI's Miami division, said he appeared to follow the correct protocol established by the Transportation Security Administration to travel with his gun.

Surveillance video shows Santiago calmly walking through the baggage claim area, pulling the handgun out of his waistband and opening fire on nearby passengers. The FBI says he then emptied one clip, reloaded, kept firing, walked outside the terminal for a moment and re-entered the baggage claim area before dropping the gun and lying down spread eagle.

Broward County Sheriff Scott Israel said he was arrested "without incident" and taken to the Broward County Jail for questioning.

Aftermath at airport

Five people were killed, including a volunteer firefighter from Virginia, a land surveyor from Iowa and a church-going great-grandmother from Georgia.

Another six people were struck by gunshots and are recovering in local hospitals. Israel said dozens of others were injured in the frantic evacuation of Terminal 2 following the shooting. That included a woman who fled into a Broward Sheriff's Office vehicle only to find a police K-9 inside, which bit her and caused minor injuries.

Israel ordered the airport closed after reports of a second shooter in Terminal 1, prompting mass evacuations that left thousands of passengers on the airport tarmac for hours. More than 12,000 passengers were taken to nearby Port Everglades for the night, and airlines continue to try to get stranded travelers home and return more than 20,000 personal items, including luggage, purses and cellphones, that were left behind in the evacuation.

Future for Santiago

Santiago was charged by the U.S. Attorney's Office in Miami with committing an act of violence at an international airport and two firearm-related offenses. Those charges could lead to the death penalty.

Piro, who is leading the investigation, has a unique history, serving as the sole interrogator of former Iraqi leader Saddam Hussein starting in January 2004. Piro has said that he has not yet ruled out terrorism in the case.

Santiago made his first appearance in a Fort Lauderdale courtroom Monday. He is being held without bond but will have a detention hearing on Jan. 17 in Fort Lauderdale.