Twitter CEO Has Sold More Than 500,000 Shares Since November

The trusts now own zero Twitter shares, after offloading more than 500,000 shares in the last two months.

That doesn't mean Costolo himself doesn't own any personal Twitter shares. He still has 36,028 Twitter shares under his name, in addition to the 509,828 restricted stock that hasn't vested yet, according to Bloomberg.

If you add up all of his stock options, his total share amounts to a little over 9 million shares.

Twitter's spokesperson said Monday's sales was part of a pre-arranged stock trading plan filed more than 90 days ago, and that Costolo still owns a large chunk of his personal shares.

"Dick has sold shares under a plan filed in the summer and his total sales represent less than 10% of his total equity in Twitter," the spokesperson said.

But Monday's sales comes at an interesting time. Twitter shares have declined nearly 45% this year, and Ev Williams, Twitter's cofounder, just sold more than 719,000 shares, worth nearly $28.7 million, last month. Jack Dorsey, too, is reported to have sold $2.1 million worth of his shares last month.

Also, back in April, Twitter executives, including Costolo, Williams and Dorsey had indicated in an SEC filing that they had no "current plans" of selling their shares, even after the company's lock up period ends. When asked about it, Twitter's spokesperson pointed to the following statement that was included in the 8-K:

"If Messrs. Dorsey, Williams or Costolo decide to sell, they are required by our policies to do so pursuant to a trading plan intended to comply with the requirements of Rule 10b5-1 of the Securities Exchange Act of 1934, as amended (a "10b5-1 Plan"). We require any 10b5-1 Plan to be entered into during an open trading window and to have a "cooling-off" period, so the earliest Messrs. Dorsey, Williams and Costolo could sell would be 90 days after our next open window."