First things first: Refuse Delivery on the package.
Just tell him that you no longer have any dealings with him. The terms and conditions of sale for your auction were clearly marked, and you will not back down. If he wishes to have any further correspondance, he can have his lawyer contact you. Warn him that any emails he sends you will be automatically filtered out, and any further correspondance directly from him will be considered harassment.
If he is really serious, then he will have his lawyer send you a letter (which will cost him a few hundred dollars). If he is bluffing, you should never hear from him again.
If he is really serious, then you have nothing to worry about. You don't even need a lawyer, this case will never hit the courts.