One of the founders of the popular messaging app, WhatsApp, posted about his departure on his Facebook account Monday, and it’s about as typical of a goodbye as it gets.

Jan Koum announced his departure on Monday via a Facebook post. He did not provide any specific reason on why he’s leaving the company, but a source told The New York Times that Koum grew concerned over the years regarding Facebook’s position on users’ data.

“It’s been almost a decade since Brian and I started WhatsApp, and it’s been an amazing journey with some of the best people. But it is time for me to move on,” Koum said. “I’m leaving at a time when people are using WhatsApp in more ways than I could have imagined.”

Foum co-founded WhatsApp with Brian Acton in 2009. Facebook acquired the messaging app in 2014 for approximately $19 billion. Both co-founders stayed with Facebook to manage the app, and during their time with the company, The Washington Post reported there were multiple clashes between them and the social media platform regarding privacy concerns and the use of ads on WhatsApp. Acton left last September to start the Signal Foundation, whose mission is to develop open source privacy technology. In March, he took part in the #DeleteFacebook campaign.

In his post, Koum said he would spend some time collecting “rare air-cooled Porsches” and playing some Ultimate Frisbee. Facebook CEO Mark Zuckerberg left a comment on Koum’s post saying, “I’m grateful for everything you’ve done to help connect the world, and for everything you’ve taught me, including about encryption and its ability to take power from centralized systems and put it back in people’s hands.”

Facebook has been under fire in recent months due to news of user data acquired by Cambridge Analytica. Zuckerberg testified in front of Congress for two days, fielding questions from senators about privacy concerns.