AP Images Warren Buffett sold more than $800 million in Apple stock last quarter, new SEC filings show. The Berkshire Hathaway CEO is Apple's biggest shareholder with a 5.4% stake worth $72 billion. Buffett's lieutenants may have sold the shares to free up cash to invest in Kroger and Biogen. Apple stock has skyrocketed 90% in the past year. Visit Business Insider's homepage for more stories. Warren Buffett sold more than $800 million worth of Apple stock last quarter, according to SEC filings published on Friday. That might seem like a massive sale, but it's closer to a rounding error for the billionaire investor and Berkshire Hathaway CEO.