A Harlem man demanded Sen. Bernie Sanders explain his relationship “with your Jewish community” at an event at the iconic Apollo Theater today.

Mr. Sanders, the only Jew to have ever won a presidential primary, held the “community conversation” as part of his outreach effort to African-Americans, who so far have delivered most of their votes to Democratic front-runner Hillary Clinton. After a panel discussion with singer Harry Belafonte, hip-hop personality Charlamagne Tha God, Erica Garner—the daughter of Eric Garner, who died at the hands of an NYPD officer in Staten Island in 2014—and former Ohio State Senator Nina Turner, the Vermont independent took two questions from the audience.

The third question, shouted from the floor, caught the Brooklyn-born pol off-guard.

“You went to Israel for a year. As you know, Zionist Jews—I don’t mean to offend anybody—they running the Federal Reserve, they running Wall Street, they’re running everything,” John Prince, who came to the event wearing a Black Lives Matter pin, yelled. “What is your relationship with your Jewish community?”

The diverse crowd at the Apollo responded with boos, and Mr. Sanders attempted to calm the visibly agitated Mr. Prince by calling him “brother.”

“No, no, no, no, no, that’s not what you’re asking. No that’s not what you’re asking. I’m proud to be Jewish,” he said to applause before pivoting to his stance on the Israel-Palestinian conflict. “I may be Jewish, but you’re not going to find any candidate running for president, for example, to talk about Zionism and the Middle East.”

“I am a strong defender of Israel, but we have got to pay attention to the needs of Palestinians,” he continued. “We’re going to have to treat both sides with respect and equality.”

Clapping and chants of “Bernie, Bernie” briefly drowned out Mr. Prince’s voice.

“They’re buying Harlem,” Mr. Prince called out.

Ms. Turner took the mic and said “we can have a conversation” on gentrification, before letting Mr. Sanders say goodbye and exit the stage. Mr. Prince continued the conversation with reporters afterward.

“If you’re in Bed-Stuy, Williamsburg, you see them—they’re playing Monopoly,” he said. “He’s part of them, yes, he’s part of them. That’s like me saying ‘I don’t want to help the blacks out when I get the presidency.”

Mr. Sanders, a secular Jew married to an Irish Catholic, had drawn applause when he mentioned his ethnicity earlier. He has not emphasized his faith much on the campaign trail.

His press secretary, Symone Sanders—an African-American Black Lives Matter activist unrelated to him—took Mr. Prince aside afterward, exchanged contact information and promised to call him.

“We can talk about it tomorrow,” she told him. “I think where we couldn’t have a conversation about it any more came is when you asserted he speaks for all Jewish people—let me finish—Barack Obama doesn’t speak for all black people, he’s the black president. Bernie Sanders cannot speak for all Jewish people, but he’s more than willing to have a conversation.”

“Why don’t we talk about the Zionist Jews that own every major corporation and media company?” Mr. Prince demanded in response. “I want to know why a 74-year-old Jewish man doesn’t want to talk about his religion.”

“When have you ever met a Jew that did not care about other Jews?” he continued

Residents of Mr. Sanders’ native neighborhood of Midwood, a conservative Jewish enclave, greeted the self-described democratic socialist with suspicion when he held a homecoming rally there yesterday.

Updated to include the exchange between Ms. Sanders and Mr. Prince.