Since mid-April, Chairman Charif Souki, Vice Chairman Walter Williams and Chief Financial Officer Don Turkleson have been forced to sell most of their holdings — including almost $2.8 million in shares for Souki — as the declining value of their Cheniere shares triggered margin calls, according to filings with the Securities and Exchange Commission. Margin calls occur when securities bought with borrowed money decline in value to the point that the brokerage demands the investor deposit more money or sell assets to offset the decline.