Activists with Black Lives Matter protests halted a political rally in Seattle where Democratic presidential candidate Bernie Sanders was scheduled to speak on Saturday afternoon.

“We’re shutting this event down — now,” said an activist who suddenly leapt on stage. She approached the microphone where Sanders had just begun speaking, thanking attendees for welcoming him to “one of most progressive cities in the United States of America.” An event organizer attempted to stop the activist, and a heated exchange ensued as the crowd booed.

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Eventually, activist Marissa Johnson was allowed to speak. “I was going to tell Bernie how racist this city is, even with all of these progressives, but you’ve already done that for me. Thank you,” she said as some in the crowd called for her arrest. Close video Are the presidential candidates serious about Black Lives Matter? Melissa Harris-Perry and her panel discuss how presidential candidates are reacting to the Black Lives Matter movement and how - if at all - their engagement is evolving. Melissa Harris-Perry and her panel discuss how presidential candidates are reacting to the Black Lives Matter movement and how - if at all - their engagement is evolving. share tweet email Embed

Johnson then asked for a four-and-half-minute moment of silence to honor Michael Brown Jr., the black teenager who was killed by police in Ferguson, Missouri, a year ago. As the crowd grew more agitated, Johnson added that Sanders says he cares about grassroots movements, but, “The biggest grassroots movement in this country right now is Black Lives Matter.”

Sanders stood by silently the entire time. Eventually, organizers decided to end the event and the Vermont senator did not return to the microphone.

“I am disappointed that two people disrupted a rally attended by thousands at which I was invited to speak about fighting to protect Social Security and Medicare,” Sanders said in a statement. “I was especially disappointed because on criminal justice reform and the need to fight racism, there is no other candidate for president who will fight harder than me.”

The face-off represented the second time in the past month that Sanders has been confronted by Black Lives Matter activists in a high-profile setting. At the liberal Netroots Nation conference in Phoenix in late July, Sanders seemed irritated after women with the movement interrupted his speech.

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In both cases, activists seemed eager not only to convey a message to Sanders, but to progressives in general. The rally in Seattle, which also featured local Democratic officials, drew thousands and was supposed to champion Social Security and Medicare.

“Bernie, you were confronted at Netroots by black women,” Johnson said, adding that he has not yet presented a criminal justice reform package like fellow Democratic candidate Martin O’Malley. She went on, entreating the crowd: “Join us now in holding Bernie Sanders accountable for his actions.”

Sanders has made efforts to address issues important to black voters since the Netroots protest. Late last month, he was warmly received in Baton Rouge, Louisiana, at a conference of the Southern Christian Leadership, the group Martin Luther King Jr. once headed. And while he has not formally rolled out a criminal justice package, he publicly acknowledged the names of black people killed by police and has begun speaking more about the issue in rallies.

The senator’s home state of Vermont is 95% white and has fewer than 7,500 black residents.

While O’Malley was also confronted at Netroots and worked hard repair relations, front-runner Hillary Clinton has yet to face a direct confrontation, even as she has made efforts to reach out to the black community.