A booking photo showing suspect Esteban Ruiz Santiago, 26, on January 7 in Fort Lauderdale, Florida. Broward Sheriff's Office via AP

Esteban Santiago, who was arrested on charges of killing five people and injuring six more in a shooting earlier this month at Fort Lauderdale-Hollywood International Airport, said he carried out the attack on behalf of the Islamic State, according to the FBI.

FBI special agent Michael Ferlazzo and other agents testified at Santiago's bond hearing on Tuesday, and Ferlazzo said Santiago had claimed to have spoken with other purported jihadis in chatrooms and websites inspired by the Islamic State, the terrorist group also known as ISIS or ISIL.

Ferlazzo did not specify whether Santiago claimed he was working directly with ISIS or had only been influenced by the group, according to CNN.

He testified that after the shooting Santiago said his mind was under some form of government control.

Santiago is charged with using and carrying a firearm during and in relation to a crime of violence, performing an act of violence against a person at an airport serving international civil aviation that caused serious bodily injury, and causing the death of a person through the use of a firearm. He could receive the death penalty for the last two charges against him and a maximum of life in prison for the first.

Santiago had been on the FBI's radar for weeks before the attack in Fort Lauderdale, Florida. FBI spokesman George Piro said that Santiago walked into an FBI office in Anchorage, Alaska, in November and told authorities that voices in his head were telling him to join ISIS.

Santiago was taken into custody at the time, admitted to a facility for medical evaluation, and given antianxiety medications, according to the Associated Press.

He was released from the facility after five days without any restrictions that might prevent him from buying or owning a firearm.

A 9 mm handgun that authorities say Santiago checked into his baggage and used to carry out the shooting was the same as one that police officers in Anchorage had seized and later returned to Santiago, Ferlazzo said.

At the hearing on Tuesday, Assistant US District Attorney Rick Del Toro said Santiago was a flight risk and a danger to the community. Santiago's attorney, Robert Berube, did not refute the claim and said his defendant was prepared to be detained throughout the trial, according to CNN.

Judge Lurana Snow ruled that Santiago be held without bond. His next hearing is scheduled for January 30.