Twitter COO Adam Bain is leaving the company

Twitter COO Adam Bain, the man in charge of the company’s entire revenue business, is leaving, according to a company filing.

CFO Anthony Noto will take over in Bain’s COO role. Noto will handle both jobs temporarily, but Twitter has already started a search to hire a new CFO to report directly to CEO Jack Dorsey. A source within the company described this search as one of Twitter’s “top priorities.”

This is a big-time loss for Twitter. Bain joined the company six years ago from Fox and has been credited with building Twitter’s entire multi-billion dollar advertising business. He’s incredibly well liked inside the company, and some even believed Bain would take over as CEO last summer when Dick Costolo stepped down.

Bain does not have another job lined up, and instead plans to take some time off before starting something new, according to a source close to the company. Bain has told Twitter’s leadership, though, that he won’t take a job at a direct competitor, like Facebook.

Twitter’s filing says that Bain resigned and “will remain at Twitter in the coming weeks” to help transition his job responsibilities to Noto.

(Reminder: Twitter’s sales org, Bain’s division, was hit hard during the company’s recent round of layoffs. So there are a lot of moving parts right now when it comes to Twitter’s ad business.)

In true Twitter fashion, Bain announced his departure with a long tweetstorm, which you can read here.

Noto will continue to run Twitter’s live video efforts, like its deals with the NFL and Bloomberg. He will also take over all revenue, sales, global partnerships and business development, according to the company’s press release.

This article originally appeared on Recode.net.