Twitter has announced a major shakeup of top executives, and several of them have left the company: senior vice president of engineering Alex Roetter, vice president of human resources Skip Schipper, vice president of global media Katie Stanton, senior vice president of product Kevin Weil and Vine general manager Jason Toff.

Chief executive Jack Dorsey made a formal announcement about Roetter, Schipper, Stanton and Weil via Twitter, after a series of stories from Recode that leaked the staffing changes over the weekend.

Dorsey said that all of the executives “have chosen” to leave. None of the executives mentioned in Dorsey’s statement immediately revealed his plans. A spokeswoman for the company declined to comment apart from what was in the statement. Dorsey also publicly thanked all of the executives for their work at the company.

Dorsey’s statement did not mention Toff, who announced separately Sunday night that he would be heading to Google to work on virtual reality in a message on his personal Twitter account.

With these top executives leaving, Dorsey said that chief operating officer Adam Bain will now oversee media, human resources and “revenue-related” products on a temporary basis. Chief technology officer Adam Messinger will take on a number of product-related duties.

Twitter, which currently has 320 million users, is under enormous pressure to kickstart user growth and prove that it can make meaningful revenue off of its users. Dorsey’s reappointment to CEO in October was praised by analysts and investors as an indication the company could refocus on its product development and make the social network more palatable to a mainstream audience. Dorsey has since launched efforts such as Twitter’s Moments feature – which offers users a digest of the network’s top-trending topics for the day – to try and make the service more user-friendly.

But investors have not been pleased with the company’s performance, sending its stock down 37 percent since Dorsey took the top job. A major outage last week sent the stock way down, to $17.73, far below its initial public offering price of $26 per share.