Stephen Colbert's talk at Harvard University was abruptly canceled Thursday after a fire alarm was pulled and hundreds of student union protesters demonstrated outside.

The event, co-hosted by Colbert and cellist Yo-Yo Ma, was stopped about 40 minutes into its question-and-answer session. The Cambridge Day reported that the fire alarm was activated, and the Harvard Graduate Student Union confirmed hundreds of protesters were outside, creating significant noise.

The union stated it was not involved in the fire alarm incident, and both the school and the fire department found no legitimate reason for its activation. "We have no knowledge of its cause," the union said in a social media post, adding that its members were relieved no one was at risk.

Before the event, the union had appealed to Ma, an alumnus, and Colbert, a union member himself, to cancel, similar to author John Green. Green had moved his event online and donated proceeds to the union, citing solidarity with the striking student workers. "It was an easy decision," Green stated. "I was sorry to do it on Zoom, but I'm also sorry the student workers have to be on strike against the richest university in the world."

The union also noted Colbert's past support for unions, including his involvement in the Writers Guild strike and co-founding Strike Force Five. "This nation owes so much to unions," Colbert had said during the writers' strike.

Rochelle Sun, a union spokesperson, expressed disappointment that Colbert and Ma crossed the picket line, despite outreach. "We believe that if they understood what we are fighting for, they might have chosen differently," Sun told the Daily Mail. "We regret that they did not take the time to engage with us beforehand, but we welcome the opportunity for dialogue now."

The Harvard Graduate Student Union began its strike on October 27, disrupting graduate classes and research. Members are seeking fair wages, safe working conditions, and the right to remain for approximately 4,000 individuals. The union has been in contract negotiations with the university for 20 months. "Harvard offered zero proposals for discussion and walked out on our members before the scheduled time ended," Sun said, referring to a bargaining session held shortly before the Colbert-Ma event. Harvard's administration has stated a commitment to reaching an agreement, with the provost and executive vice president noting offers of pay increases.