I’m not going to give an expert opinion about the theater specific rules of engagement because I would have no way of knowing that. But given my training and what is shown in the video I surmised the following:
The pilots engaged bad guys who were holding/using “weapons” (this is key).
The pilots stopped firing as soon as the bad guys dropped their “weapons” (Remember the one pilot “begging” the bad guy to pick up a “weapon” so that he could finish him off? – this is a clear indication the pilot was operating within strict rules of engagement)
The “rescue van” was not marked with the international symbols of a non-combatant. It looked exactly like a van full of bad guys.
The van full of bad guys was collecting “weapons”, their bad guy buddies, and attempting to flee the scene.
The pilots got permission to fire from a higher authority – these were not “cowboys”, but highly disciplined warriors doing their job.
So from my perspective, speaking only as a former military member, it was an appropriate course of action. You may not like this answer, but just remember that war is ugly, tragic, and hell. And also remember that if there is going to be a fight, we (the US) go to extraordinary lengths to minimize collateral damage, often putting our forces at increased risk as a result. But no matter how you look at it, war is still messy.