Microsoft on Monday hired two leading executives from the company that created ChatGPT after one of them was abruptly fired by OpenAI, the startup whose chatbot kicked off the era of generative artificial intelligence.

The developments followed a weekend of drama that shocked the AI field and fueled speculation about how the changes would shake out at OpenAI, which named a new chief executive on Friday and then replaced her on Sunday. The newest CEO vowed to investigate the firing of co-founder and CEO Sam Altman, one of the world’s most sought-after experts on AI.

Former OpenAI President Greg Brockman, also a co-founder, quit in protest after Altman was fired.

Microsoft, which has been a close partner of the company and invested billions of dollars in it, announced that Altman and Brockman would lead its new advanced AI research team.

Microsoft CEO Satya Nadella wrote on X, formerly Twitter, that he was “extremely excited” to bring on the pair and looked “forward to getting to know” the new management team at OpenAI.

In a reply on X, Altman said “the mission continues.” Brockman posted: “We are going to build something new & it will be incredible.”

Altman later added that his top priority with Nadella is to ensure that OpenAI “continues to thrive” and that it is committed to “fully providing continuity of operations to our partners and customers.”

OpenAI said Friday that Altman was pushed out after a review found he was “not consistently candid in his communications” with the board of directors, which had lost confidence in his ability to lead the company.

In an X post Monday, OpenAI’s new interim chief executive, Emmett Shear, said he would hire an independent investigator to look into Altman’s ouster and write a report within 30 days.

“It’s clear that the process and communications around Sam’s removal” were handled “very badly,” wrote Shear, who co-founded Twitch, an Amazon-owned livestreaming service popular with video gamers.

He said he also plans in the next month to “reform the management and leadership team in light of recent departures into an effective force” and speak with employees, investors and customers.

After that, Shear said he would “drive changes in the organization,” including “significant governance changes if necessary.”

He noted that the reason behind the board removing Altman was not a “specific disagreement on safety.” It was likely a reference to the debates that have swirled around OpenAI’s mission to safely build AI that is “generally smarter than humans.”

Hundreds of OpenAI employees signed a letter that began circulating early Monday calling for the board’s resignation and Altman’s return, according to a copy of the letter obtained by The Associated Press.