It was already a bad day for oil stocks with crude prices declining and interest rates headed higher, when a big stock sale from Diamondback Energy's largest shareholder pushed the Texas driller's shares down 8%, their worst day since April 2025.

The seller of nearly $2 billion of Diamondback shares was SGF FANG Holdings, the entity through which the daughter of the late Autry Stephens controls a big stake in the firm that bought her father's West Texas oil empire two years ago. The holding company sold nearly 9.1 million Diamondback shares Tuesday, trimming its stake to about 23% of the Midland, Texas company's shares, according to securities filings.

At Tuesday's closing price, the stock offering would generate proceeds of about $1.9 billion, similar to those from a sale by the holding company this past March.

Stephens, a lowkey Texas oilman, was a reluctant seller with a prostate cancer diagnosis when he agreed in early 2024 to sell his Endeavour Energy to cross-town rival Diamondback for about $26 billion. He died at age 86, the month before the sale closed that September. Lyndal Stephens Greth, his daughter, assumed leadership of Endeavor.

At the time, the shares were about $149; they closed Wednesday at $194.54.