Amazon CEO Jeff Bezos, the world’s richest person, just lost a fortune in a single evening.

Amazon reported third-quarter earnings Thursday that disappointed investors and sent Amazon stock spiraling down as much as 9 percent in after-hours trading.

In its report, the e-commerce giant gave dismal revenue guidance for the holiday shopping season, spooking investors who were expecting a huge payoff from Amazon’s growing investments across the company. A heavy investment cycle is cutting into Amazon’s profitability: Net income dropped to $2.1 billion, down 26 percent from the year-ago period’s $2.9 billion.

Amazon spent over $800 million in each of the last two quarters to expand its free one-day delivery program to more products and regions, and said it is expecting to spend $1.5 billion more on the initiative during the fourth quarter to expand its warehouse footprint and product selection.

For Bezos, who owns 57,610,359 shares of Amazon, according to the most recent SEC filing, the fall in share price equals a personal loss of nearly $6.9 billion.

If Thursday’s losses hold through Friday's market close, Bezos will lose his title as world’s richest person to Microsoft co-founder Bill Gates, according to the Bloomberg Billionaires Index.

Shares were still down by around 6 percent in Friday’s premarket.