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FORT LAUDERDALE (CBSMiami/AP) — The man accused of going on a shooting rampage inside Ft. Lauderdale-Hollywood International Airport, killing five and injuring another six, made his first court appearance in Fort Lauderdale federal court.

Just before 9 a.m. on Monday, 26-year-old Esteban Santiago, wearing a red jumpsuit and in handcuffs, was escorted out of the Broward jail into van that would took him to the courthouse.

The initial hearing Monday focused on ensuring that Santiago had a lawyer and setting future dates.

They also read the charges against him and explained the maximum penalties – charges that could put him on death row, if he’s convicted.

“They’re all very serious charges, starting with that first one violence at an international airport. That is death penalty eligible,” said David Weinstein, a former U.S. prosecutor.

Santiago is also charged with using, or carrying a firearm, during a crime of violence and causing the death of a person through the use of a firearm, both of which also carry the death penalty.

“Clear that this man is both a risk of flight and a danger to the community. It’s a very tough hurdle for his defense attorney to overcome,” Weinstein said.

CBS4’s Ted Scouten said when he walked into the courtroom Santiago was very pale and had four security officers around him. He was shackled at both his hands and feet.

Related: Travelers Caught In Chaos Of Fort Lauderdale Shooting Claim Luggage, Lost Items

Santiago kept his head down or stared directly ahead during the proceeding, giving mostly one word responses to questions. When asked about his finances and if he would be able to hire an attorney, Santiago said he only had five to ten dollars in the bank.

Authorities have interviewed roughly 175 people in the investigation, including a lengthy interrogation with a cooperative Santiago.

Santiago told investigators that he planned the attack, buying a one-way ticket to the Fort Lauderdale airport, a federal complaint said. Authorities don’t know why he chose his target and have not ruled out terrorism.

“It’s certainly an act of domestic terrorism, because it occurred at an international airport here in Fort Lauderdale,” Weinstein said. “The fact that he mentioned ISIS going into the FBI… gone into law enforcement and mentioned ISIL and other terrorist organization, that elevates it.”

Santiago spoke to investigators for several hours after he opened fire with a Walther 9mm semi-automatic handgun that he appears to have legally checked on a flight from Alaska. He had two magazines with him and emptied both of them, firing about 15 rounds, before he was arrested, the complaint said.

“We have not identified any triggers that would have caused this attack. We’re pursuing all angles on what prompted him to carry out this horrific attack,” FBI Agent George Piro said.

Investigators are combing through social media and other information to determine Santiago’s motive, and it’s too early to say whether terrorism played a role, Piro said.

In November, Santiago had walked into an FBI field office in Alaska saying the U.S. government was controlling his mind and forcing him to watch Islamic State group videos, authorities said.

“He was a walk-in complaint. This is something that happens at FBI offices around the country every day,” FBI agent Marlin Ritzman said.

On that day, Santiago had a loaded magazine on him, but had left a gun in his vehicle, authorities said. He bought his newborn child with him into the office. Officers seized the weapon and local officers took him to get a mental health evaluation. His girlfriend picked up the child.

On December 8th, the gun was returned to Santiago. Authorities wouldn’t say if it was the same gun used in the airport attack.

Santiago had not been placed on the U.S. no-fly list and appears to have acted alone, authorities said.

Santiago had been discharged from the National Guard in 2016 after being demoted for unsatisfactory performance. Bryan Santiago said Saturday that his brother had requested psychological help but received little assistance. Esteban Santiago said in August that he was hearing voices.

“How is it possible that the federal government knows, they hospitalize him for only four days, and then give him his weapon back?” Bryan Santiago said.

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.

Despite his mental evaluation, U.S. Attorney Karen Loeffler said Santiago would have been able to legally possess a gun because he had not been judged mentally ill, which is a high standard.

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