Carl Icahn has bought $500 million more in Apple Inc. (NASDAQ:AAPL) stock today. One week ago, Icahn announced that he bought $1 billion in Apple stock. Icahn was able to capitalize on Apple’s stock price drop following disappointing earnings. After this purchase, it is believed that Icahn now has around $4 billion worth of Apple stock. Icahn is using his ownership in Apple push a point for the company to increase their share buyback program. Icahn and Apple CEO Tim Cook have met in the past, but disagreed in their views of how much stock Apple should buy back. Above is a screenshot of Carl Icahn’s disclosure about the stock purchase on Twitter.