And he could legally put the weapon in his checked baggage on an international flight and then retrieve it on arrival in baggage claim without passing security.
It may not have been an international flight, per-se. It was a domestic airline flight out of Alaska. Also, you do not have to pass through security to retrieve a checked hand gun. To be able to check the hand gun, you have to declare it, you have to prove it belongs to you, that you have license to carry it both at the departure site (Alaska) and arrival site (Florida) and of course proper personal identification. The gun must be in a approved locked case to which he had the only access to. Apparently, Santiago met all the legal requirements.