- Cox started in 2005 and was one of Facebook's first 15 engineers.
- He championed improving the quality and privacy of Facebook's products, according to a former employee.
- Cox's departure comes days after CEO Mark Zuckerberg announced a drastic shift in strategy.
When new Facebook employees start at the company, there's always been one person to publicly greet them: Chris Cox.
Every Monday, Cox has welcomed new hires at the headquarters in Menlo Park, California, as part of their orientation. He would talk to them for half an hour or more, explaining Facebook's mission to connect every human in the world, according to former employees.
Cox's resignation from Facebook, which the company announced on Thursday, marks the departure of not just its chief product officer but also one of its most popular executives. One ex-employee, who asked not to be named, said Cox was viewed by many as "the heart and soul of the Facebook mission at the company."
"He was an incredible story teller and could bring you to tears when talking about new features and how important they were," a former Facebook executive told CNBC.
Cox joined Facebook in 2005, a year after the company was founded, and was one of the first 15 engineers. He's played a key role on many of its products, including News Feed, and at one point served as the company head of human resources. Facebook made him awfully rich, too. He currently owns shares worth $62.6 million, according to FactSet.
"For the average Facebook employee, Facebook without Chris Cox is almost unimaginable," the former employee said.
He also had a reputation as one of the company's big thinkers and best speakers — key reasons why he was trusted to share the Facebook ethos with its newest employees every week.
"Chris is one of the people that everybody in the company respected the most," said Henry Liu, a former strategic account manager at Facebook who left the company in 2017. "His charisma, passion for the future of communication and how he tells the story of Facebook's products really invigorated all the employees at company meetings."
Cox's departure comes just days after CEO Mark Zuckerberg announced a drastic change in strategy, saying the future of Facebook lays in private communication. The shift is notable for a company that's built one of the world's most valuable businesses on the backs of billions of users sharing their data publicly and allowing marketers to use that information to target them with advertisements.
In a goodbye post on Thursday, Cox said "This will be a big project and we will need leaders who are excited to see the new direction through."
According to Liu, "this is a sign that Facebook will be a dramatically different company in the next five to 10 years than it is today."
Another ex-employee who worked with Cox on News Feed said the former product head was always a champion of improving the quality of Facebook's tools. Cox advocated for improving privacy, reducing bugs and getting rid of fake news, even if Facebook incentivized companies based on other more growth-oriented metrics, the former employee said.
"If shipping a nice shiny feature is better than fixing a bug, an engineer is going to focus on shipping the nice shiny feature," the person said.
Facebook in February said it is changing the way it reviews the performance of its employees to focus on new criteria including "making progress on the major social issues facing the internet and our company."
"It could have been done earlier," the former employee said.