It has been an extremely rough week for billionaire Li Hejun, China’s (now former) richest man.

Hejun is the chairman of Hanergy, a solar panel firm known for producing thinner, more flexible panels than its competition.

During trading in Hong Kong on Wednesday, Hanergy stock lost a whopping 47% of its value in just 24 minutes, wiping $18.6 billion off of the company’s market value.

Hejun, who owns 80% of Hanergy’s shares, lost roughly $15 billion as a result of the monumental crash. He was worth about $30 billion before the stock collapsed.

According to CNN Money,

“Trading in Hanergy shares was halted Wednesday pending release — the company said — of an announcement “containing inside information.” The company has not commented further since, and the shares are still suspended.”

Hanergy has yet to provide any sort of explanation as to why its shares plummeted, leading to widespread confusion and speculation in the financial world. The New York-based wealth management firm Bespoke Investment went so far as to call the Hanergy debacle, “a complete mess.”

The speculation has also been fueled by the fact that Hejun was absent from the company’s annual shareholder meeting on Wednesday, though a spokesman said that he was attending the opening of Hanergy’s new clean energy exhibition in Beijing instead.

Hanergy’s stock crash comes on the heels of unprecedented success for the company and its chairman. CNN Money reports:

“Before Wednesday’s plunge, Hanergy’s shares had surged 625% over the past year, making it seven times bigger than First Solar, the top U.S. solar firm. At its peak in April, the company was worth more than $45 billion, allowing Li to overtake Alibaba co-founder Jack Ma as China’s richest man.”

The Hanergy disaster was followed by another major crash in the Hong Kong stock market just a day later.

On Thursday (5/21), shares of Goldin Financial and Goldin Properties — firms owned by Hong Kong billionaire Pan Sutong — plummeted more than 40%. Bloomberg estimates that the twin companies have lost about $21 billion in market velue over the past two days.

Read more from CNN Money and Bloomberg.

BONUS: Hejung lost $15 billion in 24 minutes — that means he was losing $625 million per minute, or roughly $10.4 million every second.