What do I do? Please help!?

I was advertising online that I wanted one of those cats that looks like a wildcat, but it is perfectly legal and they are tame. One guy e-mailed me and said he'd offer me a genuine cheetah cub for 2,000 dollars, and sent me a picture of a baby cheetah. It was so cute, and I looked it up it was four weeks old. But I know it's ILLEGAL and cheetahs are endangered, so what do I do? I only have his e-mail address, how do I report him?