Brother of suspect questions why he was able to keep gun

The brother of the man suspected of carrying out the Fort Lauderdale airport shooting has questioned why Esteban Santiago was allowed to keep his gun after US authorities knew he had become increasingly paranoid and was hearing voices.

The 26-year-old reportedly had trouble controlling his anger after serving with the US National Guard in Iraq, and told his brother that he felt he was being chased and controlled by the CIA through secret online messages.

Speaking to FBI agents in Alaska, where he lived, Santiago had reportedly told them the government was forcing him to watch so-called Islamic State group videos.

When Santiago told agents at the FBI field office his paranoid thoughts in November, he was evaluated for four days, and then released without any follow-up medication or therapy.

"The FBI failed there," Bryan Santiago said, adding: "We're not talking about someone who emerged from anonymity to do something like this."

"The federal government already knew about this for months, they had been evaluating him for a while, but they didn't do anything."