(CNN) A large group of conservative donors and scholars were shocked last weekend after a friendly exchange between Vice President Mike Pence and Dick Cheney, the former vice president, turned tense.

Cheney, a fierce defender of the foreign policy of President George W. Bush, politely questioned the approach of Pence's boss, President Donald Trump, on foreign policy and national security.

Two people who attended the March 9 event, which took place at the American Enterprise Institute's annual off-the-record retreat in Sea Island, Georgia, confirmed the exchange to CNN, which was first reported by the Washington Post

The string of critical questions from Cheney injected drama into what is normally a staid affair. Afterward, Cheney and Pence became the top item of discussion among the mix of Trump-supporting and Trump-skeptical conservatives attending the retreat.

After asking Pence a few prepared and cleared questions, Cheney began expressing his concern about Trump's approach to the major foreign policy issues of the day. "He was persistent," said one attendee of Cheney. "He just kept coming at him on North Korea, treatment of the allies, the NATO payment issue."

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