Agreed on a trade with a member yesterday morning. I shipped the knife as agreed about an hour later, less then 24 hours ago. When shipped I immediately provided tracking as always. I get nasty emails this morning accusing me of not sending the knife and threatening me with all sorts of things. When entering both our tracking numbers on the USPS mobile site I get messages that the system is down. I sent him a pic of the receipt and he says that proves nothing and he is opening up all sorts of cases and more threats. Keep in mind I mailed this less then 24 hours ago and i have done a couple dozen perfect transactions here. He says he no longer wants to communicate. I have copies of all the correspondance and postal receipt and he keeps making threats. What should I do?