WhatsApp co-founder, CEO, and Facebook board member Jan Koum announced today that he will be leaving Facebook. The news comes after Washington Post eported that Koum would leave due to disagreements with Facebook management about WhatsApp user data privacy and weakened encryption. Koum obscured that motive in his note that says "I'll still be cheering WhatsApp on – just from the outside."

Koum, who sold WhatsApp to Facebook for more than $19 billion in 2014, also plans to step down from Facebook’s board of directors. The date of his departure isn’t known.

Koum’s exit is highly unusual at Facebook. The inner circle of management - and the Board of Directors - have been fiercely loyal during the scandals that have rocked the social media giant. In addition, Koum is the sole founder of a company acquired by Facebook to serve on its board. Only two other Facebook executives - Zuckerberg and Chief Operating Officer Sheryl Sandberg - are members of the board.