The Army veteran's rambling walk-in interview at the Anchorage office was concerning enough for authorities to take away his gun an
d order a mental health evaluation. But it wasn't enough to get him mentally adjudicated, which would have prohibited Santiago from owning a firearm.
Santiago got the gun back a month later when he retrieved the pistol from police headquarters, and it was that weapon, law enforcement sources told CNN, that he used in the airport attack.
http://www.cnn.com/2017/01/08/us/fort-lauderdale-airport-shooting-main/
So he was in a mental health facility for 2 weeks. And they knew what he told the FBI. And the knew he left his newborn in a car in freezing temps, along with a gun, which he was waiting to retrieve. Knowing all that, he was still not 'mentally adjudicated.'
See below:
According to federal regulations, a person has been “adjudicated as a mental defective” if a court, board, commission or other lawful authority has determined that he or she, as a result of marked subnormal intelligence, or mental illness, incompetency, condition, or disease: 1) is a danger to himself, herself, or others; or 2) lacks the mental capacity to contract or manage his or her own affairs.3 The term “adjudicated as a mental defective” explicitly includes a finding of not guilty by reason of insanity or incompetence to stand trial.4