SAN FRANCISCO (Reuters) - Facebook Inc’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 that his departure came “with great sadness.” He had left a graduate program at Stanford University to join Facebook in 2005 as a software engineer and helped developed 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, in what technology analysts expect will be a complicated engineering task.

Shares of Facebook were down 1.7 percent in extended trading following the announcement.

Cox informed the company of his intention to resign on Monday, according to a regulatory filing on Thursday.

Also departing is WhatsApp Vice President Chris Daniels, adding to a string of recent high-profile exits from Facebook’s product and communications teams. The shakeup 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.

Slideshow ( 3 images )

Daniels had informed the company several months ago of his intention to leave and will stay on through a leadership transition, a person familiar with the matter said.

Zuckerberg told Wired magazine on March 6 that “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.”

NEW STRUCTURE

Will Cathcart, vice president of product management, will now lead WhatsApp, and Head of Video, Games and Monetization 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. And growing viewership and advertising on videos are of growing importance to both the Facebook and WhatsApp apps.

Slideshow ( 3 images )

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.

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 until Monday he spoke at the orientations for new employees.

Daniels, who had worked on Facebook initiatives in developing countries, had 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 shortly after Cox, as well as decade-long veterans Chief Technology Officer Mike Schroepfer and engineering Vice President Jay Parikh.