Investigators are pursuing all angles to determine why suspect Esteban Santiago opened fire in the baggage claim area of Florida’s Fort Lauderdale airport, killing five people and wounding eight others.

The FBI said terrorism has not been ruled out, but family members say the Iraq war veteran had a history of mental health issues.

“We will be pursuing every angle to try to determine the motive behind this attack,“ special agent in charge of FBI’s Miami Office George Piro said. He added that they were reviewing the suspect’s recent movements.

The suspected shooter took a flight from Anchorage, Alaska to Fort Lauderdale, with a handgun in his checked luggage. After retrieving his bag, witnesses said he began firing indiscriminately before running out of ammunition.

“This was a tough day for our state,” Florida Governor Rick Scott told reporters. “Clearly a senseless, evil act happened, where according to law enforcement five individuals have lost their lives and we know there are still people fighting for their life. The… What’s important to me is that we will never tolerate things like this in our state. Whoever’s responsible, we’ll do everything we can to hold them accountable”.

It is the latest in a string of mass shootings in the US, one of the deadliest took place last June when a gunman killed 49 people at a gay nightclub in Orlando, Florida.