Sotheby's announced Thursday Bill Ruprecht will step down as CEO and chairman of the art auction house. Ruprecht, who has been in charge for 14 years, plans to resign in mutual agreement with the company. Sotheby's has already started searching for a new CEO, Forbes reported, and Ruprecht will stay on until one is found. After the announcement, Sotheby's shares increased 7 percent Thursday.

The company's board of directors plans to work with lead independent director Domenico De Sole and company Spencer Stuart to find a replacement. “Under Bill’s leadership, the Sotheby’s brand has never been stronger,” De Sole said in a statement. "As we move to new leadership, the Board is sharply focused on upholding the world-class standard of excellence that Sotheby’s has long represented to our clients and achieving Sotheby’s full long-term potential for the benefit of our shareholders.”

The news comes about six months after billionaire Dan Loeb joined the board of directors after calling Sotheby's "an old master painting in desperate need of restoration," Business Insider reported. Loeb criticized Ruprecht for not keeping up with changes in auction trends: Sotheby's didn't expand its online presence fast enough, and it didn't reach out to newly wealthy potential buyers abroad.

Last week, Sotheby's sales were bested by rival auction company Christie's. Christie's got $852.9 million. Sotheby's, which had pieces from Andy Warhol and Mark Rothko, brought in half that. But those events didn't affect Ruprecht's jobthe New York Times reported. His resignation has been a long time coming -- the board of directors started discussing a leadership shake-up in August. It finalized its decision Thursday.

“The last few years have been the most successful in the company’s history," Ruprecht said in a statement. "I am comfortable and confident saying Sotheby’s is well-positioned for the next chapter of its success and I will do all I can to contribute to a smooth leadership transition.”