Brian Acton, who made billions when Facebook acquired messaging app WhatsApp, has stated that it is time for users to begin deleting their accounts on the social network.

Fortune reports that Brian Acton, the co-founder of the now Facebook-owned messaging app WhatsApp, has called on Internet users to delete the app following the recent user data scandal. After it was revealed that the user data of approximately 50 million Facebook accounts were allegedly compromised via a personality quiz, Facebook is now facing calls for regulation across the U.S. and UK, and a lawsuit from investors.

Acton tweeted on Tuesday night that it was now time to “#DeleteFacebook”, a hashtag which has since become popular across the internet:

Acton worked as an engineer and executive at Yahoo before co-founding WhatsApp in 2009, the app was purchased by Facebook in 2014 for the sum of $19 billion. Acton is now the head of the Signal Foundation, a direct competitor to WhatsApp despite WhatsApp using Signal’s open-source, end-to-end encryption technology for some time. Signal founder Moxie Marlinspike announced the launch of the Signal Foundation last month, the foundation is a non-profit partly funded by Acton who has invested $50 million in the foundation.

“Brian left WhatsApp and Facebook last year, and has been thinking about how to best focus his future time and energy on building nonprofit technology for public good,” Marlinspike said when launching the foundation. “The addition of Brian brings an incredibly talented engineer and visionary with decades of experience building successful products to our team.”

Acton is not a regular user of Twitter, only tweeting twice this year and twice in 2016. One of Acton’s most interesting tweets regarding Facebook is from 2009, which seems to relate to the company “turning down” Acton.

Facebook turned me down. It was a great opportunity to connect with some fantastic people. Looking forward to life's next adventure. — Brian Acton (@brianacton) August 3, 2009