In that case, what's wrong with calling it just a plain old accident? I don't understand why we have to find fault with all accidents. There are degrees in which some are unavoidable.
If everyone can just walk away with the lessons that they learned, finding fault is often unnecessary.
In this case, the pranksters were charged with a wide array of felonies, not just related to stealing the decoy deer, but to the accident itself.
If placing blame is necessary, then the factors need to be weighed and the blame needs to be laid at the feet of all those responsible so that the results are just rather than simply driven by emotion.