If the person who won has functioning brains, he or she will go completely silent. We will never find out who they are. If I'm winning, I'm telling everyone I know that I'm going to be going silent for a while and that I'll call them every now and again to confirm that I'm safe and okay. They'll never be able to contact me unless I have a proxy or I'm using a burner phone. Money can COMPLETELY change people you thought you knew and can be as much of a curse as a blessing.
Look up the post by blakeclass. It's long but worth the read as a practical guide for what you do if you suddenly find yourself holding millions.