(CNN) --It's become a phenomenon -- an anonymous person giving away cash by the handful and leaving clues on Twitter.
Alexandra Eherton was across the street, when she saw a tweet from an account named @HiddenCash, and she recognized an image of the 9th circuit courthouse in the Twitter clue.
She ran to find an envelope.
"There was 60 dollars in twenties and then about four just two dollar bills."
She's part of a growing club of people who've found cash in envelopes by following clues.
"We got the tweet saying go to the caterpillar by the water,” explained Matthew Burkert, who also found some cash. "My first thought was caterpillar construction equipment."
A friend knew about a bulldozer, beached along the highway.
So did somebody else Matthew had to race him.
"He went up the front side of the caterpillar, I went up the back side, and it just happened to be on the back side.'
Burkert explained that as they talked, another clue was tweeted out.
“It shows a little chef -- and a beach....so I’m guessing Baker's Beach," said Burkert.
Off they went, although they got there a moment too late.
It all leaves people wondering “why?”
"I think he's just trying to have fun giving away money.”
"Is it fun?"
"Setting aside the purpose for a second, the "result" of these hidden cash hunts is just as int. running after money could easily inspire greed. But this seems to have inspired generosity."
"Hi did you want twenty dollars?"
Within five minutes, this couple gave all the money away to families on the beach.
"Do you want 60 dollars?"
Burkert says he, too, wants to pay it forward.
"Giving it out to people on the street, I don't know but definitely not gonna use it for myself."
And in an anonymous phone interview, the man behind hidden cash says that’s the point. The Twitter handle says that this is an "anonymous social experiment for good."
The person also told one reporter that there are plans to expand this to other cities, starting with Los Angeles and then New York City.
"I’m in that one percent that some people loathe. But rather than hating people who are successful, my point would be to encourage people who have been successful to give back a little bit more,” the man behind the giveaways said.
At least one person did keep the cash.
"Yeah, I’m a writer, and I don't make that much money."
Better known by her pen name, An Irvano bought copies her own books with the money, hoping to sell them and help launch her career.
"What would you have done if you had found the person who did it?"
"I would've gotten on my knees and thanked them."