Buffett also leaves Abel and Berkshire Hathaway with a tremendous stockpile of cash. Buffett began selling stocks last year ahead of the market sell-off, while also ending the company's buyback program. Together with increased operating profits, Berkshire ended the first quarter with a whopping $347.7 billion in cash on its balance sheet.

Berkshire Hathaway stock reacted early Monday after Warren Buffett surprised shareholders with the announcement he would step down.

"You're losing one of the most esteemed investors one could argue of all time," a source said of investors' reaction to Buffett's plan to step down.