Ah, but this is (retroactively) unintended killing.
Imagine a car being hit from the air by a Predator drone because analysis wrongly believes it's full of terrorists. Intended killing. They later realise they made a mistake a killed some family. Now it's unintended killing. Not much of a difference there by my reckoning.
Except that the scenario you've described is not collateral damage. According to the U.S. Air Force:
"Broadly defined, collateral damage is unintentional damage or incidental damage affecting facilities, equipment or personnel occurring as a result of military actions directed against targeted enemy forces or facilities."
If a Predator blows up a car and the family traveling inside it because some intelligence analyst believes it's full of terrorists, that is killing, pure and simple. There's no "collateral" here. If during the same strike, another car with another family is accidently destroyed by the blast, that is, indeed, collateral damage.
To summarize, if you destroy what you're targeting, there's no collateral damage. If you destroy something other than what you're targeting, then there's collateral damage. Collateral damage is unintended killing, but not all unintended killing is collateral damage. Hence, your argument is fallacious.
collateral damage — Unintentional or incidental injury or damage to persons or objects that would not be lawful military targets in the circumstances ruling at the time.
