On Friday, the board of OpenAI, the buzzy AI company behind viral chatbot ChatGPT, suddenly and publicly ousted its CEO Sam Altman. The announcement came one day after he appeared publicly on behalf of his company at Thursday’s APEC CEO Summit.

OpenAI’s board said it conducted “a deliberative review process” and that Altman “was not consistently candid in his communications with the board, hindering its ability to exercise its responsibilities.”

“The board no longer has confidence in his ability to continue leading OpenAI,” the board’s statement continued.

As of this week, OpenAI’s six-person board included OpenAI co-founder and President Greg Brockman, who was also chairman of the board; Ilya Sutskever, OpenAI’s chief scientist; Adam D’Angelo; Tasha McCauley; Helen Toner; and Altman himself. The company began publicly posting its board’s member list on its website in July, after the departures of LinkedIn founder Reid Hoffman, director of Neuralink Shivon Zilis and former Texas congressman Will Hurd.

Here’s a rundown of the board behind the controversial shake-up:

Greg Brockman: An OpenAI co-founder, Brockman quit his role at the company on Friday in protest of Altman’s ousting, saying publicly, “Sam and I are shocked and saddened by what the board did today.” Brockman spent five years as CTO of Stripe before moving on to help launch OpenAI. In 2020, Brockman said OpenAI’s top obstacle in its first five years was the idea that making the full extent of the startup’s work public wasn’t necessarily beneficial for humanity, in his eyes. At the time, he said, “We realized that as these things get powerful, they’re dual-use…and that we as technology developers have a responsibility to not just say, ‘Hey, we built this thing, it’s up to the world to decide how to use it.'”

Ilya Sutskever: As of now, Sutskever is the sole remaining OpenAI co-founder on the board. After co-founding DNNResearch — an AI startup focused on neural networks — and selling it to Google, Sutskever joined Google as a research scientist and stayed for nearly three years before moving on to OpenAI as a co-founder and research director. Since November 2018, he’s been the company’s chief scientist.

Adam D’Angelo: The current CEO of Quora, a social platform for questions and answers, D’Angelo spent nearly four years at Facebook and was CTO of the tech giant from 2006 to 2008. He is not an employee at OpenAI.

Tasha McCauley: McCauley, who is not an OpenAI employee, is on the board of directors of both OpenAI and GeoSim Systems, a geospatial tech company. She is an adjunct senior management scientist at Rand Corporation and has been on the OpenAI board since 2018.

Helen Toner: Toner is a board member and non-OpenAI employee who spent time at the University of Oxford’s Center for the Governance of AI, and has been a director of strategy for Georgetown’s Center for Security and Emerging Technology for nearly five years. Last year, Toner told the Journal of Political Risk that, “Building AI systems that are safe, reliable, fair, and interpretable is an enormous open problem… Organizations building and deploying AI will also have to recognize that beating their competitors to market— or to the battlefield — is to no avail if the systems they’re fielding are buggy, hackable, or unpredictable.”

Earlier this year, Microsoft’s expanded investment in OpenAI — an additional $10 billion — made it the biggest AI investment of the year, according to PitchBook. In April, the startup reportedly closed a $300 million share sale at a valuation between $27 billion and $29 billion, with investments from firms such as Sequoia Capital and Andreessen Horowitz. Despite its significant investment, however, Microsoft has no board seat at OpenAI.

“While our partnership with Microsoft includes a multibillion-dollar investment, OpenAI remains an entirely independent company governed by the OpenAI Nonprofit,” OpenAI has publicly stated. “Microsoft has no board seat and no control. And… AGI is explicitly carved out of all commercial and IP licensing agreements. These arrangements exemplify why we chose Microsoft as our compute and commercial partner.”

Microsoft had no new comments to add on Saturday and requests for comments from board members weren’t immediately returned to CNBC.

OpenAI’s product feature announcements earlier this month showed that one of the hottest companies in tech has been rapidly evolving its offerings in an effort to stay ahead of rivals like Anthropic, Google and Meta in the AI arms race.

ChatGPT, which broke records as the fastest-growing consumer app in history months after its launch, now has about 100 million weekly active users, OpenAI said this month. More than 92% of Fortune 500 companies use the platform, up from 80% in August, and they span across industries like financial services, legal applications and education, according to Mira Murati, OpenAI’s CTO-turned-interim CEO.

The news of Altman’s ousting comes after OpenAI’s Dev Day, the company’s first in-person event, on Nov. 6, which also included a surprise appearance by Microsoft CEO Satya Nadella.

“The systems that are needed as you aggressively push forward on your road map require us to be on the top of our game, and we intend fully to commit ourselves fully to making sure you all… have not only the best systems for training and inference, but also the most compute,” Nadella told Altman while onstage together at Dev Day. He added, “That’s the way we’re going to make progress.”

On that day, Altman told Nadella, “I think we have the best partnership in tech and I’m excited for us to build AGI together.”

As recently as last month, OpenAI was reportedly in talks to close a deal that would lead to an $80 billion valuation. When CNBC asked OpenAI COO Brad Lightcap about that deal, he declined to comment.

At OpenAI’s Dev Day, in response to a CNBC question about GPT-5, Altman said, “We want to do it, but we don’t have a timeline.”