A federal grand jury on Thursday indicted Esteban Santiago, the man accused of killing five people inside a Fort Lauderdale airport earlier this month, authorities said, according to CNN.
Santiago is charged with numerous counts and could face death or life in prison.
Federal authorities said Santiago, 26, wounded six others when he opened fire in the baggage claim area of the Fort Lauderdale-Hollywood International Airport, aiming at victims' heads and bodies until he ran out of ammunition.
Santiago was confronted by a Broward County Sheriff's deputy and dropped his weapon before being arrested.
He was charged following the attack with an act of violence at an international airport resulting in death, as well as with two firearms offenses.
Santiago, who lived in Alaska, told FBI agents he carried out the January 6 attack on behalf of the Islamic State (ISIS), an FBI agent testified at Santiago's bond hearing last week.
The agent did not elaborate on whether Santiago was purporting to be linked to ISIS or simply inspired by the terrorist organization.
Federal authorities in Alaska said Santiago told them before the attack that he was hearing voices and that his mind was being controlled by the CIA. He also made similar claims during an interrogation after the shooting.
Once he was transferred to the FBI office in Miramar, Florida, he introduced the ISIS claim and has not mentioned mind control, the agent testified, according to CNN.
The agent, who conducted the interview in Miramar, said only that Santiago claimed to be fighting for ISIS and that he'd been in touch via jihadist chat rooms with like-minded people who were also planning attacks.
ISIS has not claimed responsibility for the attack.