Hundreds of peaceful demonstrators carrying signs that read "Hate Speech Is Not Free Speech" had been protesting for hours before the event.
In the evening, a small group dressed in black and in hooded sweatshirts used metal barricades to break windows, threw smoke bombs and flares, used a diesel generator to start a large bonfire outside the building.
The demonstrators were met by tight security in the form of law enforcement armed in riot gear. A shelter in place order was in effect and the Cal campus was placed on lockdown. Source
In spirit, a few degrees away from the protests of the 1960's.