Facebook CEO Mark Zuckerberg announced to the company's employees changes in some of the company's leading executives, as the social netwok is organized to build out a privacy-focused social platform.

CEO Mark Zuckerberg reiterated that the company is organizing around a "privacy-focused" emphasis on private messaging, which he announced last week.

After working for Facebook for more than 10 years, Chris Cox is leaving the company. Cox has played many central roles at Facebook — starting as an engineer on Facebook's original News Feed, building the company's first HR teams, leading Facebook's product and design teams, running the Facebook app, and most recently overseeing the strategy for the Facebook family of apps.

Zuckerberg said that Cox "help us chart a course for our family of apps going forward," adding that "we have a clear plan for our apps, centered around making private messaging, stories and groups the foundation of the experience, including enabling encryption and interoperability across our services."

Chris Daniels, who has been running Facebook's business development team, leading Internet.org, and most recently worked on WhatsApp, is also leaving Facebook.

"While it is sad to lose such great people, this also creates opportunities for more great leaders who are energized about the path ahead to take on new and bigger roles," Zuckerberg said.

Will Cathcart will be the new head of WhatsApp. He was running the Facebook app.

In addition, Fidji Simo will be the new head of the Facebook app. She has played key roles in building many aspects of the Facebook app, including leading Facebook's work on video and advertising.

Facebook's family of apps strategy has been led jointly by Chris Cox and Javier Olivan. Javi will now lead identifying where Facebook's apps should be more integrated.

"Since we have now decided on the basic direction of our family of apps for the next few years, I do not plan on immediately appointing anyone to fill Chris’s role in the near term. Instead, the leaders of Facebook (Fidji Simo), Instagram (Adam Mosseri), Messenger (Stan Chudnovsky), and WhatsApp (Will Cathcart) will report directly to me, and our Chief Marketing Officer (Antonio Lucio) will report directly to Sheryl," Zuckerberg added.

"This is an important change as we begin the next chapter of our work building the privacy-focused social foundation for the future, " Zuckerberg said.