The Jan. 6 shooting took place at a baggage claim at the Fort Lauderdale-Hollywood International Airport and targeted "newly-arrived passengers retrieving their luggage", according to federal prosecutors. Investigators say he continued until he ran out of ammunition, then dropped his weapon and was arrested by law enforcement officers.
The five people killed in the attack were in Fort Lauderdale for cruise vacations.
Federal Bureau of Investigation agents testified that Santiago confessed to planning the massacre and told investigators he traveled to South Florida to carry it out. Santiago could face the death penalty if convicted. He affirmed to the judge that he understood each of the charges against him - which include 10 homicide-related counts and several firearms violations.
While Santiago told Federal Bureau of Investigation agents he was motivated by ISIS, law enforcement have found no evidence to support his claims and the indictment includes no terrorism charges.
A trial date has not yet been set.
Brunhilde Pomsel, former secretary of Nazi propagandist, dead at 106
Brunhilde Pomsel, the secretary to Nazi Germany's propaganda chief Joseph Goebbels, has died in Germany at the age of 106. After the war she spent five years in Soviet detention camps, and was released in 1950.
Seltzer repeatedly emphasized the victims' names as he read the entire indictment aloud, according to The Associated Press.
He is being held without bail on charges of causing death or bodily harm at an global airport, causing death during a crime of violence and using a firearm during a crime of violence.
Santiago, who served in Iraq from 2010 to 2011, had a history of erratic behavior.
The FBI previously said Santiago visited its office in Anchorage past year complaining about hearing voices and supposed Central Intelligence Agency mind control, which led to Anchorage police temporarily seizing his gun and Santiago's brief stay in a mental hospital. He sought help from the Federal Bureau of Investigation in Anchorage, Alaska, last year, saying he was having "terroristic thoughts".