fter the best month for stocks since 1987, markets abruptly sank on Friday as companies revealed dwindling profits squeezed by the coronavirus, and as U.S.-China trade tensions ramped up again. In a stark reminder of the pandemic's power to shift markets, the S&P 500 and Dow Jones Industrial Average each ended the day down 3%, with declines hitting some of the world's richest tycoons especially hard. Ten billionaires’ fortunes plummeted a staggering $26 billion on Friday alone, an unraveling of their prior month’s gains.

Following days of positive quarterly earnings reports and lofty stock gains for the billionaires behind Google, Microsoft MSFT and Facebook, Amazon AMZN was among the first to turn the tide late Thursday. Shortly after closing at a record high, Amazon reported earnings that missed Wall Street estimates — despite record first-quarter revenues of $75.5 billion.

Amazon's outlook also put Wall Street on edge after disclosing plans to spend an estimated $4 billion on Covid-19 related efforts, including on protective gear for employees and higher wages for hourly teams.

“If you're a shareowner in Amazon, you may want to take a seat, because we're not thinking small,” Founder and CEO Jeff Bezos said in the earnings announcement. "Providing for customers and protecting employees as this crisis continues for more months is going to take skill, humility, invention, and money."

Amazon shares sank 8% as a result on Friday, tanking its founder’s fortune. Bezos’ net worth fell $10.6 billion, erasing two weeks of gains from rising Amazon stock, which hit record highs amid surging consumer demand as a result of the pandemic. The firm’s second-quarter earnings forecast now includes the possibility of a net loss; the firm hasn't had a quarterly loss since 2015.

Jeff Bezos’ ex-wife, MacKenzie Bezos, was also hit. Her fortune fell $3.7 billion on Friday, the day's second-largest drop among billionaires. She's now worth $44.8 billion.