Vice President Joe Biden addresses the White House Summit on the United State of Women in Washington, Tuesday, June 14, 2016. Associated Press/Cliff Owen Hedge-fund billionaire Bill Ackman made the mistake of heckling Joe Biden as Biden discussed his late son at a recent dinner.

And the way Biden responded shows his personality is still fiery as ever.

The former vice president was speaking at a private dinner during last month's SALT conference in Las Vegas. At one point, former presidential candidate Jeb Bush, also in attendance, asked Biden why he didn't run in the 2016 election, according to a Fox Business account published Friday.

Biden reportedly responded by talking about his late son Beau Biden, who died in 2015 from brain cancer, and the room fell silent, according to the account. Biden then stopped himself.

"I’m sorry … I've said enough," he said.

That's when Ackman intervened with an apparent attempt at a joke:

"Why? That’s never stopped you before," he said.

Biden didn't take kindly to Ackman's jab. From Fox Business:

The formal, and understated dinner conversation suddenly turned tense, according to three people who were present and confirmed both the substance and the wording of Biden’s responses. Biden, these people say, turned to someone seated near him, and asked, "who is this a--hole?," a reference to Ackman. Then he turned directly to Ackman and stated: "look, I don't know who you are, wisea--, but never disrespect the memory of my dead son!” these people say. Ackman attempted what was described as an apology, to which Biden said, "just shut the hell up."

A spokesman for Ackman downplayed the interaction, but didn't refute Biden's language.

Biden's near-candidacy was a popular topic at the SALT conference. In one speaking appearance that week, Biden publicly said of Hillary Clinton: "I never thought she was a great candidate. I thought I was a great candidate."

But it took until Friday for news of the Ackman incident to surface.

"Biden was in rare form," a source told Fox Business. "I can’t believe it has never leaked out."

The former vice president has not ruled out a 2020 White House bid.

EDITOR'S NOTE: New York Magazine has since published a statement from the SALT organizers denying Fox Business' account of the event. Citing four people who were in attendance, New York Magazine reported that Biden made no mention of his son in the exchange with Ackman, and that Biden had been talking about President Donald Trump before his verbal tie-up with the Wall Street investor.