Just reading about this aggravates me beyond belief, and then seeing the pictures of the dead animals is the icing on the cake.
You shipped to him, right? You have his name and address then, I assume? I hope you also saved the vet records to further prove that these animals were very ill.
If I were you (and you can take this advice or leave it), I would write to him one last time. I would tell him that unless he rectifies the situation immediately by sending your animals back, you will:
1. File a complaint with the police department for theft. He knowingly and willingly scammed you, you can provide proof of that; he stole X amount of dollars from you as a result. When you call to file the police report, they will ask you if you want to take him to court or press charges. Say YES.
2. Report him to the BBB.
3. File an animal cruelty report with the ASPCA or Humane Society; if they can't do anything, you will contact his local Animal Control department to make sure something is done.
Tell him that you will provide pictures of the abuse to the three above-referenced entities; you will provide pictures and emails to show he did not send you what you paid for (he can't back his case up with shabby excuses, either - as a breeder I'm sure he is well-qualified enough to know what he sent you was NOT what you ordered).
Furthermore, you can threaten to take him to small claims court to get your money (or animals) back. If he says he already sold/gave away your animals, or that they died (in which case you'd have even more of a case against him), you can still try and get your money back regardless.
And if he threatens to get even with you, assure him that upon any investigation, they'll find he made false claims and will be in even more trouble.
Sound excessive? Probably. The point of threatening him with all this is to "hope" he will just give you your animals back so he doesn't have to endure several painful processes. Of course, if he doesn't, depending on how badly you want your animals/money back, you can then follow through with what I mentioned above.
Just what I would do if I were in your situation.
PS - Just a note, when and if you do write to these people, keep in mind that proper grammar and punctuation, and clear, concise, well-thought out sentences will add to your credibility.