NEW YORK (AP) — Jan Koum, the CEO of WhatsApp, is leaving the company and Facebook.

Koum confirmed on his Facebook page on Monday that he's leaving, saying it is time for him to "move on." His messaging app is known for protecting the privacy of its users using strong encryption.

Facebook CEO Mark Zuckerberg commented that he will "miss working closely" with Koum. Facebook is reckoning with the worst privacy crisis in its history, not to mention questions over how it handles user data and, broadly speaking, whether it is good for the world.

Facebook bought WhatsApp for $19 billion in 2014. Back then, Koum wrote that the deal wouldn't have happened if WhatsApp "had to compromise on the core principles that will always define our company, our vision and our product."