Washington (CNN) Bernie Sanders' presidential campaign apologized to a group of pro-Palestinian student activists who were booted from a campaign rally in Boston and threatened with arrest.

The activists, members of Boston Students for Justice in Palestine, showed up at the Saturday rally with a large banner asking "Will ya #Feel the Bern 4 Palestine??!" before a campaign staffer asked them to either leave the event or put the sign away. A police officer then told the students to leave or they would be arrested.

The students posted video of the interaction online.

Sanders' spokesman Michael Briggs confirmed the incident Tuesday and said campaign manager Jeff Weaver called the activists "and apologized to them."

"They shouldn't have been excluded," Briggs said. "It was an overreaction by an over-eager staffer who didn't show good judgment."

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