College graduation is usually a time of celebration, but Sunday’s commencement at Stanford felt the impact of the national outrage surrounding Brock Turner, a former student sentenced to only six months in jail for sexually assaulting an unconscious woman in 2015. Some graduating Stanford students chose to protest Turner’s sentence at the ceremony, wielding signs criticizing Turner’s light sentence and calling out the pervasive rape culture that troubles so many college campuses.

Stanford graduation ceremonies traditionally feature a “Wacky Walk,” in which graduating students walk through the school’s football stadium wearing silly costumes. According to The Washington Post, this year’s ceremony included students dressed as astronauts, dinosaurs, crayons, lions, and flappers. However, in the wake of Turner’s sentencing, some students skipped the costumes and instead carried signs with messages like “Teach your son not to rape” and “Brock Turner is not an exception.” Some students wore papers with “1/3” printed on them attached to their mortarboards — a reference to the World Health Organization’s estimation that more than a third of women worldwide will experience physical or sexual assault in their lifetimes.

“The goal is to amplify the voices of survivors on campus,” explained Brianne Huntsman, a graduating student and one of the organizers of the protest. She told The Los Angeles Times, “There is this idea that there is just, quote-unquote, one Stanford rapist, that Brock Turner is the Stanford rapist. And from our work on campus, we really know that this is not the case.”

GABRIELLE LURIE/AFP/Getty Images

GABRIELLE LURIE/AFP/Getty Images

GABRIELLE LURIE/AFP/Getty Images

Ceremony attendees also saw the protest take to the air. UltraViolet, a women’s advocacy group, hired a plane to fly overhead bearing a banner that read, “Protect survivors. Not rapists. #PerskyMustGo,” referencing Santa Clara Superior Court Judge Aaron Persky, who handed down Turner’s lenient sentence.

GABRIELLE LURIE/AFP/Getty Images

Although most of the graduating seniors did not participate in the protest, Turner's case and the increased awareness of rape and rape culture it has created did find its way into the commencement itself. University President John Hennessy began the ceremony with a moment of silence honoring survivors of sexual assault and the victims of Saturday’s mass shooting in Orlando. Documentary filmmaker Ken Burns delivered the keynote speech, and laid down a simple truth: “If someone tells you they have been sexually assaulted, take it effing seriously and listen to them.”