Antifa members prepare for confrontation during a rightwing No-To-Marxism rally on August 27, 2017 at Martin Luther King Jr. Park in Berkeley, California. Amy Osborne/AFP/GETTY

Five people including one police officer were injured during a counter-protest in Berkeley, California, Sunday, marking the fifth time this year that the city has seen violence during protests. Two were hospitalized. University of California in Berkeley has long had a history of protest-culture and is the birthplace of the Free Speech Movement.

A right-wing “No to Marxism in America,” protest was planned for Sunday, and then called off, but still saw a limited attendance. A much larger counter-protest dubbed the “Rally Against Hate,” also took place Sunday. Though largely peaceful, an element of the counter-protest inflicted violence on supporters of President Donald Trump and the right-wing protest, according to the Washington Post Monday.

The attacks were perpetrated by all-black clad antifa,” short for anti-fascists. Antifa is a loose collection of people who oppose fascism and racism and aren’t afraid of violence. Many people who identify as antifa are also anarchists. The attacks included one person who was repeatedly kicked and punched and others were hit with pepper spray and paint.

In all, 13 people were arrested for various charges stemming from the protest and counter-protest, including one person arrested for assault with a deadly weapon, according to the Associated Press.

“I applaud the more than 7,000 people who came out today to peacefully oppose bigotry, hatred and racism that we saw on display in Charlottesville,” said Berkeley Mayor Jesse Arreguín in a statement. “The violence that small group of protesters engaged in against residents and the police, including throwing smoke bombs, is unacceptable. Fighting hate with hate does not work and only makes each side more entrenched in their ideological camps.”

Fear of violence has weighed heavy on the minds of officials after the death of one woman in Charlottesville, Virginia, earlier this month. A far-right rally which included a large element of neo-Nazis and white supremacists ended in tragedy when a man with alleged white supremacy ties drove a car into a group of counter-protestors, killing the woman.

Berkeley has been a hot bed of protests and counter-protests in the age of Trump. A speech planned by the far-right provocateur, Milo Yiannopoulos, at the University of California in February was canceled due to violence by protesters, including antifa members. There was a March pro-Trump march that was marked by several injuries and ten arrests. Two protests in April saw some violence, one taking place on the 27th over the cancellation of a talk by right-wing commentator Ann Coulter was the most peaceful.

In 1964, the University of California at Berkeley gained international attention when the school moved to shut down political activism by people tabling and handing out pamphlets on a sidewalk on school property. This birthed the Free Speech Movement. The school eventually relented and allowed the activism.​