Billionaire investor Warren Buffett said Saturday that he wants to step down as chief executive of Berkshire Hathaway at the end of the year. The revelation came as a surprise because the 94-year-old had previously said he did not plan to retire.

Buffett, one of the world’s richest people and most accomplished investors, took control of Berkshire Hathaway in 1965 when it was a textiles manufacturer. He turned the company into a conglomerate by finding other businesses and stocks to buy that were selling for less than they were worth.