AKIPRESS.COM - Esteban Santiago, 26, opened fire in Fort Lauderdale airport after flying from Alaska with a gun in his luggage killing five people and injuring 6 more. 

During the later mental health evaluation, he told the FBI he was hearing voices and believed he was being controlled by a US intelligence agency. 

But the authorities found no wrongdoing and gave back the confiscated gun.

Karen Loeffler, the US attorney for Alaska, told journalists: "As far as I know this is not a person that would have been prohibited from having a gun."

She explained that federal law only allows for gun rights to be taken away from someone on mental health grounds if they are "adjudicated mentally ill".

FBI agent George Piro said earlier that the suspect had travelled to Fort Lauderdale specifically to carry out the attack.

There was no sign of any altercation on the flight or at the airport before the attack began, Mr Piro said.

Federal charges have been filed against Mr Santiago and they should be outlined in detail later on Saturday, BBC reported.

Mr Piro said: "We continue to look at all avenues and all motives for this horrific attack. We are continuing to look at the terrorism angle in regards to the potential motivation."