I was in the room when Warren Buffett said he was stepping down. The mood went from shock and disbelief to gratitude.

• I was in the room when Warren Buffett announced his plans to step down as CEO of Berkshire Hathaway.
• The audience was shocked but rallied to give the investor two standing ovations.
• The Berkshire Hathaway chief said he'd informed neither his board nor his successor ahead of time.

I was in the room when Warren Buffett said he would step down as CEO at the end of this year, marking the end of a remarkable tenure that has lasted nearly six decades.

The legendary investor and Berkshire Hathaway boss made the surprise announcement in the closing minutes of a nearly five-hour-long Q&A on Saturday at his company's annual meeting in Omaha.

The packed stadium was stunned into silence. The longest-serving S&P 500 CEO, who took the top job in 1970 and built Berkshire from a failing textile company into a $1 trillion company known around the world, was stepping down.

It seemed as if Buffett, who is 94, might continue for a few more years still, given how mentally sharp he seemed throughout the morning as he fielded questions about everything from tariffs and Berkshire's huge cash pile to government spending and life advice.

He revealed that he had informed neither Berkshire's board, apart from two of his three children who are directors, nor his planned successor sitting next to him, Greg Abel.

Once Buffett finished speaking, the crowd leapt to its feet to deliver thunderous applause for a man who meant so much to so many of them.

Buffett's thousands of shareholders rose again and clapped as he prepared to leave the stage, leading him to joke that their praise could be interpreted either as admiration or relief that he was resigning.

The atmosphere turned to sadness and disbelief as onlookers processed what had just happened and its historical significance began to take hold.

Conversations broke out once Buffett left the stage and the lights came up as the reeling attendees turned to one another to parse the news. There was a steady drone in the stadium as people talked through their emotions and the consequences of the announcement.

Nirav Panchmatia, 50, a financial literacy coach from India was attending his eighth Berkshire meeting and had brought along his 10-year-old daughter, Parthavi, for the first time.

He described the moment that Buffett broke the news as "extraordinary" and said he felt "sad" that Buffett would no longer be CEO, but it was a "wonderful experience" to have been in the room when he stepped down.

He said he hopes Buffett will still host at least another meeting or two in the years ahead.

Dennis Wong, 58, a private investor from Canada, told BI he's owned Berkshire stock for nearly a decade.

"I just witnessed history," he said. "I'm so thrilled to be here personally."

Wong said the news "does rock the entire financial industry and markets," and applauded Buffett for assuring investors of a smooth transition by saying he would remain involved at Berkshire and available to help Abel.

He compared Buffett to Tom Brady in football, Wayne Gretzky in hockey, and Steve Jobs in tech. "When it comes to investing, Buffett is certainly the GOAT," using the acronym for "greatest of all time."

Buffett said that while his successor would have the final word, he assured the audience that he would likely "still hang around and conceivably be useful."