Fourteen-year-old Tatiana Ramirez was tearful after pulling an envelope full of dollar bills from a flowerbed of bluebells at the foot of a tree outside a Los Angeles shopping centre.
A secretive millionaire, who uses the Twitter name @HiddenCash, began leaving packets of money around San Francisco a week ago before moving on to Los Angeles, posting clues to the location of envelopes to his more than 300,000 followers on the social network.
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Hidden cash hunt moves to LA
An anonymous millionaire using the twitter handle @HiddenCash is leaving packets of money around Los Angeles, moving the hunt on from San Francisco where it started a week ago.
"There's $US210 in here," she told London's The Sunday Telegraph moments later. "When I found it I started shaking and I couldn't stop.
"I keep thinking this is a dream, I can't believe it. I'm going to use it to help my family because my parents don't have a job and my sisters can't get a job."
On Thursday night, Tatiana was the first person to find one of several stashes placed by a mystery Samaritan who has become a social media phenomenon.
A self-described member of the "1 per cent" of wealthiest Americans, he calls his gifts an "anonymous social experiment for good" and encourages finders to share the money with those around them.
The amounts involved are not life changing - no more than $1000 a day is given away - but many Californians have become obsessed with locating the mini-windfalls.
They have been left in hiding spots including an arugula pot, a disused bulldozer and a public lavatory.
Before Tatiana made her discovery, thousands of people descended on Burbank, a suburb of Los Angeles, when they deciphered the clue: "Sounds like where a robin or eagle might keep their money." As one cash hunter quickly concluded, "Burbank=Birdbank".
For the next five hours, Burbank, home to Walt Disney Studios, was full of adults and children glued to mobile phones waiting for the next clue to arrive. When it did, they all converged on a vast shopping mall called the Empire Centre.
"I hope there is not a lot of hysteria," Mr "Hidden Cash" had said.
In the event, there was mass hysteria.
As more clues dropped, the hordes swarmed like ants over a bus shelter, dug up the earth with their hands, ripped apart rubbish bins, rummaged in bushes and clambered up trees, as a fleet of four news helicopters hovered overhead.
"This is madness," shouted one man while another took the safety cover off a street lamp and started rifling through the electrical wires looking for free money.
Suspicions have mounted that the whole phenomenon may be a clever marketing ploy by a yet to be revealed company or advertising agency.
But Mr "Hidden Cash" has rebutted that accusation, saying on Twitter: "Why is it so hard for some to believe that genuine acts of generosity are possible with no ulterior motive? Are we so jaded? Love."
He already has several copy-cats in America and one in Britain, who began by leaving £50 ($90) in an envelope behind a grit bin in Leeds.
In a series of anonymous interviews, Mr "Hidden Cash" has said that he is aged between 35 and 45 and is a property developer who recently made $US500,000 "flipping" a single house in San Francisco.
He said: "There is nothing commercial behind this. I've made millions of dollars the last few years, more than I ever imagined, and yet many friends of mine, and people who work for me, cannot afford to buy a modest home. This is my way of giving back to the community and also having fun."
Dr Wendy Walsh, a human behaviour expert, said the experiment had tapped into something deeper than people's simple desire for money, which explained the hysteria over amounts of cash that were relatively small.
"This is a little bit of good news for once," she told London's The Sunday Telegraph.
"Every human being carries a rescue fantasy of a fairy godmother, a shining prince, a man in armour, and it's a micro-version of that. A lot of people are on a treadmill and this is something different that's off the grid, that brings happiness and fun.
"What I like about this guy's idea is the paying it forward, encouraging people to use it. A wealthy individual can give money to a big charity but this is putting power in the hands of people."
Chris Treicheo, a production supervisor who found $US135 in an envelope taped to the pavement at the Empire Centre, said: "I want to thank him. I was at work a few blocks away when the clues started coming in and I decided to give it a whirl.
"I think this is really fun, so long as no fights break out. I'm going to put the money in the bank."
After abandoning her search, Chantal Khalilieh, 22, said: "It doesn't matter I didn't find the money, I had a blast looking."
Several kilometres away from the Empire Centre, there was minor damage as cash hunters trampled though flower beds near a fountain after Mr "Hidden Cash" posted a picture of it.
"It's not here," shouted Sergio Spinal, 28, on his knees peering under a seat at a bus stop near the fountain while his wife Clara, 35, shone a light for him.
"The clue said the money would be 'sitting here waiting' so I thought about the bench at the bus stop," he said.
Mr and Mrs Spinal and their children Joyhan, eight, and Sophia, nine months, had driven 20 miles to join the frenzied crowd.
He said: "My wife wanted to buy a little jumper machine for our baby today so that's what I'd use the money for."
Karla Bonilloa, 15, was with her mother Maria, 49, peering under a rose bush with a torch.
She said: "I was doing my homework when we saw the picture of the fountain. It took us 30 minutes to get here by car so I hope we're not too late. If I find the money I'll use it for education.
"I think the guy doing this is awesome."
The Sunday Telegraph, London