By going into San Francisco to investigate “communist subversion,” the House Committee on Un-American Activities was entering the proverbial hornet’s nest. And the hornets — although resolutely nonviolent ones — were ready. Several hundred students gathered outside the courthouse and city hall, as one of their own was subpoenaed to testify, along with a Berkeley professor. The Committee certainly did not do themselves any favors when they issued “white cards” for those deemed sympathetic to enter to courtroom. But what made it truly memorable was the violence that would erupt shortly later.

On this day, May 13, in 1960 a squad of police turned fire hoses on a Berkeley group at the steps of the courthouse. While that got them back away from the building, it apparently served only to agitate to the protesters. A waiting police force tore into the crowd, swinging billy clubs and rounding up whoever they could into waiting police wagons.

The Committee would claim the riot was communist-sponsored, but reports and footage at the scene showed well-dressed, well-behaved, seemingly middle-class students. With most of the arrested set free, San Francisco’s protesters were only emboldened to speak up louder against injustices wherever they say. The “Black Friday” event was the precursor to the free speech movement of the mid-1960s.