So. Even if they were lawful combatants and we were at war (neither of which is true,) It is a war crime to issue an order of no quarter. (that is to say, ordering that no prisoners be taken, and that all enemies must be killed.)
it's nazis shit through and through. They're not lawful combatants, and we're not at war. Even if they were smuggling, that doesn't allow them to be blown out of the water with impunity. And they've not been demonstrated to be smuggling, never mind, smuggling into the US.