Richard Spencer, white nationalist and self-described leader of the alt-right movement, gave an abbreviated speech at the University of Florida in Gainesville on Thursday afternoon.

In response to the event, which took place at the university’s Phillips Center for the Performing Arts, groups from around the state rallied to protest Spencer.

Many audience members booed Spencer and shouted over his speech. Protestors chanted phrases like "Go home, Spencer!" and "Say it loud, say it clear, Nazis are not welcome here!"

"What are you trying to achieve then?" Spencer asked the crowd, according to ABC News. "You all have an amazing opportunity to be a part of the most important free speech event perhaps in our lifetime. This is when the rubber hits the road with the question of the First Amendment."

Amid concerns that the protests could turn violent, Gov. Rick Scott, R-Fla., signed an executive order on Monday to declare Alachua County, where both Gainesville and the university are located, in an “imminent threat of potential emergency.”

There was also a provision to activate the National Guard, if needed.

Sen. Marco Rubio, R-Fla., via Twitter asked “Gator Nation” to “embarrass [Spencer] by denying him the attention he craves” ahead of the speech.

More than 500 campus police -- the most in the university's history -- were on site during the event, University of Florida President W. Kent Fuchs told Fox News. The Florida Highway Patrol also monitored the event, as did police from other college campuses in the state, he said.

Overall, the university spent more than $500,000 to increase security.

Ahead of Spencer's speech, Fuchs was unclear about the exact number of people who were planning to either attend or protest the event, but said that those who show up in favor of Spencer should be “moderate in number.”

Fuchs encouraged anyone affiliated with the university to stay away from the event, warning that protesting would “draw attention to him [Spencer] and create what he wants,” he said.

As a public institution, the university cannot deny Spencer from renting a facility on the campus to host his event, as that would violate his First Amendment right to free speech. However, Fuchs did emphasize Thursday that “no one invited him, and the University of Florida is not sponsoring or hosting him.”

“He has given us [the university] a platform as well -- we can talk to the media about the value of inclusion at our school,” Fuchs added. “We understand what he represents and how it goes against our values.”

Who is Richard Spencer?

Spencer, who said his speech was intended to “wake up white Americans and white people around the world,” leads the National Policy Institute (NPI), a think tank located in Virginia that was founded in 2005. The think tank promotes an “alternative right” agenda. It also publishes a journal called Radix, which promotes white culture and identity, according to the Anti-Defamation League.

Spencer, 39, became president of the NPI in 2011 after its founder, Louis R. Andrews, passed away, according to the Southern Poverty Law Center (SPLC). Spencer is also the American editor of AltRight.com, a site he launched in early 2017 that promotes an alt-right agenda.

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Spencer, who grew up in Dallas, has a bachelor’s degree from the University of Virginia and a master’s degree in humanities from the University of Chicago. He later dropped out of a Ph.D. program at Duke University.

His education background helps him to promote his “image-conscious” strategy that appeals to educated, middle-class whites, according to the SPLC.

Why is he controversial?

There are numerous controversies surrounding Spencer.

Spencer’s main goal as a leader of the “alt-right” is to create an all-white America -- something he has called a “peaceful ethnic cleansing.” Critics have called Spencer an anti-Semite and a racist, among other terms.

According to the Washington Post, in a 2013 speech Spencer said “we need an ethno-state so our people can 'come home again,' can live amongst family and feel safe and secure.”

Spencer has rejected being labeled a Nazi, racist or white supremacist -- telling the Washington Post in 2016 that he prefers to be called an “identitarian.” In the same interview with the newspaper, Spencer was asked about his plans to create an ethno-state, a way of thinking that has been paralleled to Adolf Hitler.

“Look, maybe it will be horribly bloody and terrible,” he said at the time. “That’s a possibility with everything.”

The Anti-Defamation League has called Spencer a "symbol of the new white supremacy." Spencer has rejected conservatism and has instead envisioned a “new” right that embraces a “white racial consciousness.”

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Spencer gained media attention after a 2016 video of him saluting nearly 200 attendees at the National Policy Institute's annual conference went viral.

In the video, Spencer can be heard saying “Hail Trump, hail our people, hail victory!” Many attendees can be seen giving Spencer the Nazi salute in return.

Spencer, whose speeches at Texas A&M and Auburn University have sparked protests, also participated in a white nationalist rally in Charlottesville, Va., in August to protest the city’s removal of a statue of Robert E. Lee.

The event, which was met by counter-protesters, turned violent when a white nationalist protester drove a car into the crowd and killed one woman.

Spencer, along with other white nationalists, returned to Charlottesville earlier in October to hold a torch-lit rally to once again protest the statue’s removal.