Things went a bit awry last month at a Hong Kong Polytechnic University graduation ceremony when the university president refused to shake hands with graduates wearing masks, however, that was nothing compared to what happened on Thursday at the Chinese University of Hong Kong.

Prior to the university’s graduation ceremony, more than 1,000 students took part in a march on campus in which they wore masks, dressed in signs, held up signs, and walked up steps featuring posters of Carrie Lam’s face for them to step on them.

At some point, a man, who claimed to be a student from mainland China, confronted the protesters, singing the Chinese national anthem while pointing a knife at the crowd. He was escorted away by security.

A Mandarin-speaking man holding a knife sang the national anthem in front of graduates at the Chinese University of Hong Kong. He said he wanted to protect himself before being detained by security. Video: SCMP/Martin Choi pic.twitter.com/CDy2f0wOUm — SCMP Hong Kong (@SCMPHongKong) November 7, 2019

When the ceremony started and the anthem began to play, some students defiantly turned their backs and tried to drown out “March of the Volunteers” by shouting out slogans like “Liberate Hong Kong, revolution of our times!” and “Five demands, not one less!”

Eventually, the university decided to cut the ceremony short due to “special circumstances.”