Facebook’s chief product officer and one of its earliest employees Chris Cox said on Thursday he is leaving the company just days after chief executive Mark Zuckerberg revealed a plan to transform the world’s biggest social network into an encryption-focused messaging company. Cox, the 36-year-old Zuckerberg lieutenant who would have managed the CEO’s vision to bring Facebook, Instagram and WhatsApp closer together, said in a blog post his departure came “with great sadness”. He left a graduate programme at Stanford University to join Facebook in 2005 as a software engineer and helped develop its original news feed feature. “As Mark has outlined, we are turning a new page in our product direction, focused on an encrypted, interoperable, messaging network … This will be a big project and we will need leaders who are excited to see the new direction through,” Cox said in a Facebook post. Cox’s departure removes a layer of management, bringing Zuckerberg closer to a family of apps that he wants to make compatible, which could be a complicated engineering task. Facebook shares were down 1.7 per cent in extended trading following the announcement. Cox told the company he was resigning on Monday, according to a regulatory filing on Thursday. Also departing is WhatsApp vice-president Chris Daniels, adding to a string of high-profile exits from Facebook’s product and communications teams. The shake-up is the second major management restructuring in as many years as the company also faces numerous government investigations across the world related to user privacy and fake news on its services. Daniels told the company several months ago he was leaving but would stay through a leadership transition, a person familiar with the matter said. Zuckerberg told Wired magazine on March 6 “there will be a bunch of work inside the company to make sure that we have the right folks in the right roles” to bring Facebook’s apps together and introduce more privacy features. EMarketer analyst Jasmine Enberg said that “whenever there is a shift in strategy, it’s not unusual to see some personnel changes”. Will Cathcart, vice-president of product management, will now lead WhatsApp, and head of video, games and monetisation Fidji Simo will be the new head of the Facebook app, Zuckerberg said. Cathcart and Simo worked closely to bring video uploading tools and professional video content to Facebook. Growing viewership and advertising on videos are of important to Facebook and WhatsApp apps. The company does not immediately plan to fill Cox’s role, Zuckerberg said, adding that Cathcart, Simo and the heads of Instagram and Messenger will now report directly to him. Facebook’s family of apps strategy has so far been led jointly by Cox and Javier Olivan, vice-president of growth. Facebook at 15: Zuckerberg, privacy, fake news and China Zuckerberg said on Thursday that Olivan will now lead the effort to integrate Facebook apps, a key move as the company encrypts conversations on more of its messaging services and makes them compatible. Cox gained greater oversight of WhatsApp and Instagram following the exits of their founders over the last two years. He also remained a key figure at Facebook, where for years he spoke at orientations for new employees. Facebook CEO Mark Zuckerberg promises a more privacy-friendly company, sort of Daniels, who worked on Facebook initiatives in developing countries, moved a year ago to WhatsApp, which is more popular than Facebook in many big emerging markets. A WhatsApp spokesman declined to comment on Daniels’ departure or make him available for comment. Zuckerberg still has a number of long-time product and engineering lieutenants. They include hardware vice-president Andrew Bosworth, who joined soon after Cox, as well as decade-long veterans Chief Technology Officer Mike Schroepfer and engineering vice-president Jay Parikh.