American tech entrepreneur Sam Altman said the only life experience he could compare to his resignation as CEO of OpenAI was the loss of his father, Business Insider reported.

“The only life experience I had that was much worse was when my father died,” Altman said in an interview on a podcast hosted by American TV host Trevor Noah.

Altman called his resignation, announced by OpenAI’s board on Nov. 18, “incredibly painful” and drew several parallels to his father’s death in 2018. According to New York Magazine, Altman’s father was 67 when he died of a heart attack.

“It was so unexpected that for a short time I had to pick up the pieces of his life. And it wasn’t until a week after that that I had a moment to catch my breath and think, ‘Oh my God, I can’t believe this happened,'” he told Trevor Noah about his father’s death.

“So it was much worse,” Altman said, adding that he felt “echoes” of his father’s death at the time of his firing from OpenAI.

Sam Altman is working on a new board at OpenAI

The artificial intelligence research company announced on Nov. 22, after days of intense turbulence, that Altman would return as CEO and elect a new board of directors to serve.

The announcement comes just two days after Microsoft, a major financial backer, said it had hired Altman in a shock move that further rocked sentiment at OpenAI.

Immediately after the announcement made by the company founded by Bill Gates, more than 500 of OpenAI’s 770 employees threatened to resign in an open letter if the company’s board of directors, which was the source of the crisis, did not resign.

The employees said they would leave Microsoft “en masse”, from the division that was supposed to be headed by Sam Altman.

OpenAI has an atypical governance structure in which the board of directors consists mostly of outsiders rather than its founders and investors.