The official at the Securities and Exchange Commission who heads the division responsible for oversight of the securities markets and exchanges is leaving the agency.
The SEC says Robert Cook, director of the trading and markets division since January 2010, is stepping down. Cook oversaw several initiatives taken by the SEC aimed at reducing risk in the markets. He also led the SEC staff's investigation of the market "flash crash" of May 6, 2010, when the Dow Jones industrial average dropped nearly 600 points in five minutes.
Wednesday's announcement on Cook followed word on Tuesday that the director of another SEC unit, the corporation finance division, is leaving. Meredith Cross has headed it since June 2009.
SEC Chairman Mary Schapiro announced recently that she is stepping down next week.