Background: Shapiro was born in Los Angeles, California. His family is Jewish, having immigrated in part from Russia. Skipping two grades (third and ninth), Shapiro went from Walter Reed Middle School to Yeshiva University High School of Los Angeles where he graduated in 2000 at age 16. He graduated summa cum laude and Phi Beta Kappa from the University of California, Los Angeles in 2004, at age 20, with a Bachelor of Arts degree in political science, and then cum laude from Harvard Law School in 2007.
Context: On February 25, 2016, Shapiro gave a speech at California State University, Los Angeles, entitled "When Diversity Becomes a Problem". Shapiro's speech focused on how the concepts of microaggressions and safe spaces were being used to suppress free speech in the name of diversity of skin color, while ignoring the value of diversity of thought. In response to the announcement of the speech, hosted by the campus's chapter of Young Americans for Freedom, student protesters demanded that the speech be cancelled, labeling it as "hate speech". The university's president, William Covino, eventually announced the cancellation of the speech three days before it was to take place, with the intention of rescheduling it so that the event could feature Shapiro debating someone with opposing viewpoints. In response to the cancellation, Shapiro said he would be attending the event anyway, and several lawsuits were threatened against the university for canceling the speech. As a result, Covino ultimately backed down and allowed the speech to go on as planned. The day of the speech, hundreds of student protesters formed human chains to block the doors to the theater where the event was to be held, shoving away anyone who attempted to enter and starting several fights in the crowded lobby. Some students were ultimately able to enter the theater by being sneaked in through back doors, though the protesters soon found out and barricaded those doors as well. Shapiro eventually made it into the theater and began his speech, only for a fire alarm to be pulled by one of the protesters; Shapiro continued speaking regardless, calling Covino "cowardly" and referring to the protesters as "spoiled brat snowflakes" and "fascists". After the speech ended, Shapiro had to be escorted out a secret exit by police and his own bodyguards, while those inside the theater were told that they could not leave since the protesters were preventing anyone from leaving. Only after Shapiro left did the protesters eventually disperse, and those inside the theater were allowed to exit. Three months after the CSULA incident, Young America's Foundation announced on May 19 that it was filing a lawsuit against the university (with Shapiro as one of the plaintiffs), claiming that the First and Fourteenth Amendment rights of the students were violated by Covino's attempted cancelation of the event, as well as the physical barricading of students from entering or leaving the event, and the encouragement of such actions by several campus professors. CANNOTANSWER
Question: What did the protesters do?. Whats the answer?

those inside the theater were told that they could not leave since the protesters were preventing anyone from leaving.