Twitter CEO Jack Dorsey is stepping down as chief of the social media company, effective immediately. Parag Agrawal, the company's chief technology officer, will take over the helm, the company said Monday.

Shares of Twitter were down about half a percent before noon on Monday.

Dorsey, 45, was serving as both the CEO of Twitter and Square, his digital payments company. Dorsey will remain a member of the Board until his term expires at the 2022 meeting of stockholders, the company said. Salesforce President and COO Bret Taylor will become the Chairman of the Board, replacing Patrick Pichette, a former Google executive, who will remain on the board as chair of the Audit committee.