Kevin Systrom and Mike Krieger, co-founders of the Instagram app, have reportedly decided to leave the company over disagreements with Facebook CEO Mark Zuckerberg. Sources cited by Bloomberg News on Monday night said the pair became aggravated with Zuckerberg’s growing day-to-day involvement as he increasingly relies on Instagram to boost Facebook growth. Systrom and Krieger sold the photo-sharing network to Facebook for $1 billion in 2012. At that time, the app boasted 30 million users; today, it has more than 1 billion and serves as a main source of Facebook revenue. Zuckerberg issued a statement praising Systrom and Krieger as “extraordinary product leaders.” “I’ve learned a lot working with them for the past six years and I’ve really enjoyed it,” he said, adding that he’s looking forward to “seeing what they build next.” The exits come after Jan Koum, founder of WhatsApp, another Facebook acquisition, announced he was leaving over concerns about the parent company’s position on user data.