Black Lives Matter protesters interrupted a planned Seattle rally for Democratic presidential candidate Bernie Sanders on Saturday afternoon, preventing the Vermont Senator’s scheduled speech on Social Security and Medicaid from taking place.

Sanders, who previously was interrupted at Netroots Nation by Black Lives Matter protesters, was asked to come to the microphone to be held accountable. Protesters motioned him over, saying Sanders has “yet to put out a criminal justice reform package like O’Malley did”.

The protesters listed grievances against school disparities, gentrification and police violence in Seattle before requesting a moment of silence to commemorate the one year anniversary of Mike Brown being killed by law enforcement in Ferguson, MO.

While many in the crowd remained silent for the four and half minutes, many others cursed and booed for the protesters to get off the stage.

Black Lives Matter activist demands silence from booing @SenSanders crowd before she speaks #BernieinSeattle pic.twitter.com/Scdk6zVKmn — Jim Brunner (@Jim_Brunner) August 8, 2015

Sanders left the stage without responding to the grievances or giving his prepared speech. He later posted this press release on his website.

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. 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 organizers of the protest warned Sanders and other candidates of the urgency to not just discuss, but present solutions for systemic issues facing Blacks in America. In a statement issued later, the BLM Seattle chapter said, “Presidential candidates will not win Black votes without putting out an explicit criminal justice reform package. As was said at the Netroots action, presidential candidates should expect to be shut down and confronted every step along the way of this presidential campaign.”