Climate change activists in Spain marked their nation’s Columbus Day on Sunday by vandalizing a historic mural of Christopher Columbus at Madrid’s Naval Museum.

Two members of the environmental group “Futuro Vegetal,” meaning “Vegetarian Future,” were caught on video throwing red paint at the 1892 painting First Tribute to Christopher Columbus by Spanish artist José Garnelo. The activists also unfurled a banner that read, “October 12, nothing to celebrate. Ecosocial justice,” according to the Spanish outlet El País.

Spain honors Columbus on October 12, while the date in the US falls on the second Monday of the month. The holiday commemorates, in part, Spain’s funding of Columbus’s 1492 voyage that led to the European discovery of the Americas.

After throwing the paint, the activists were confronted by security guards and museum visitors who pulled them away. The pair were detained by museum security and later arrested. Authorities charged them with crimes against cultural heritage.

A spokesperson for the group said that Columbus Day “celebrates centuries of oppression and genocide against the indigenous people of Abya Yala,” which is the indigenous term for the Americas.

A separate sit-in also took place Sunday at Madrid’s Reina Sofía Museum.

Columbus Day continues to face opposition from left-wing activists, who often refer to it as Indigenous Peoples Day instead. President Donald Trump last week signed a proclamation declaring Monday Columbus Day, calling it an effort to “reclaim” Columbus’s “extraordinary legacy of faith, courage, perseverance, and virtue.” The President previously vowed in April to bring the holiday “back from the ashes,” and said he would reinstate “Columbus Day under the same rules, dates, and locations, as it has had for all of the many decades before!”