Transcript for Mystery Millionaire Gives Away Money Using Twitter
street in San Francisco? There is free money. Who knew? A mystery millionaire is leaving cash all over San Francisco. And he's leaving clues on Twitter. He's about to head to other cities around the U.S. And nick watt has the story. Reporter: There really is a guy in San Francisco giving away free money. Hiding it under benches. Taping it to parking meters. Posting clues on Twitter, like this. Forrest Hanson found 100 bucks and shared it with fellow beachgoers. Who is this mysterious robin hood? How much are you going to give away? Probably going to reach at least in the hundreds of thousands. Reporter: He's a real estate developer. Won't tell us his name. Just getting him on the phone took a lot of cajoling. How rich are you? It's in the millions. I don't know. Samantha cane found a stack of Jacksons in a doggy dirt bag dispenser. Makes you feel like a kid again. Reporter: Alfe found a $20 in a bike rack. I donated it to AIDS lifecycle. Reporter: That jives with our mystery millionaire's mission. I do like giving something back. And I wish more people would. Reporter: I'm feeling warm and fuzzy. But I'm also a professional cynic. Can you promise me, this isn't a marketing ploy? I'm not selling potato chips or any other product whatsoever. Reporter: He is splashing the cash in L.A. This weekend. Then, New York. Then, who knows? He could be coming to a city near you. Watch out. For "Good morning America," nick watt, ABC news, Los Angeles. The man behind the hidden cash just tweeted overnight, that he's on his way to San Jose to give away money tomorrow. I'm on a flight after this. What a great virus to get started. Hoping everybody else was going to pick it up and giving the money away, as well. He hopes it creates momentum. And if you're in line for a cup of coffee, buy the person behind you coffee. Who doesn't love a treasure hunt. What's not exciting is the
This transcript has been automatically generated and may not be 100% accurate.