At a Clinton campaign rally in Omaha on Monday, billionaire investor Warren Buffett challenged Donald Trump to a game of rich guy “you show me yours and I’ll show you mine,” offering to exchange tax returns with the Republican nominee at “any time, any place.”

“I’ve got news for him, I’m under audit too,” said Buffett, according to Politico. “I’ll bring my tax return. He can bring his tax return. Nobody is going to arrest us.”

Trump has previously refused to release his tax returns because they are currently under audit, an explanation the IRS has basically dismissed as bogus. From Politico:

“There are no rules against showing your tax returns and just let[ting] people ask questions about the items that are on there,” Buffett said, before asking the boisterous crowd, “How many of you would be afraid to have your tax return made public?”

“You’re only afraid if you got something to be afraid about. He’s not afraid of the IRS. He’s afraid because of you. I will meet him in Omaha or Mar-a-Lago or he can pick the place,” Buffett offered. “We’re both under audit. And believe me, nobody will stop us from talking about what’s on those returns. Send the word to him, if you will.”

Buffett went on to criticize Trump’s treatment of Khzir and Ghazala Khan, parents of Army Captain Humayun Khan, saying, “Donald Trump and I haven’t sacrificed anything.”

“No member of the Buffett family has gone to Iraq or Afghanistan. No member of the Trump family has gone to Iraq or Afghanistan,” said Buffett. “How in the world can you stand up to a couple of parents who have lost a son and talk about sacrificing because you were building a bunch of buildings?”

“When I heard that, my mind went back—and this goes back before most of you were born—but they went back to the McCarthy hearings,” Buffett continued. “McCarthy went on and on, implying this guy was a communist and doing all kinds of things. And finally, Joe Welch couldn’t take it anymore and he said and I’ll quote him, ‘Have you no sense of decency, sir?’ I ask Donald Trump: ‘Have you no sense of decency, sir?’”