No, that would not have been legally "justified". Perhaps the sheriff won't arrest or pursue it, but that's a different question, and has no bearing on a civil wrongful death lawsuit.

I'd also be concerned about knowing if the guys at the site are even authorized to give away scrap. They may think they are if they don't plan to use it, but the owner may disagree. If I knew who the owner is that's great, otherwise I'd shy away from a "sure, help yourself" response.