Maja Hitij | Getty Images News | Getty ImagesTesla CEO Elon Musk’s trust sold 639,737 shares in the electric vehicle company on Thursday totaling about $687 million, according to regulatory filings made public Friday. Shares of the company were down more than 2% in early morning trading and about 15% week to date.The news comes days after Musk and his trust sold roughly $5 billion worth of the stock.Before the initial sale, Musk asked his millions of Twitter followers whether he should sell 10% of his Tesla stock and said he would follow the results. That poll was supported by about 58% of those who responded. But, some of the shares were sold in part to satisfy tax obligations related to an exercise of stock options.Musk still owns more than 167 million shares of Tesla.Musk indicated earlier this year that he was likely to sell “a huge block” of his options in the fourth quarter. During an appearance at Code Conference in September, he said when his stock options expire at Tesla, his marginal tax rate would be over 50%.- CNBC’s Lora Kolodny and Christine Wang contributed to this report.