Less than two days after students at the University of Missouri successfully forced the resignation of the school's chancellor and the university system president, police say they have arrested a 19-year-old suspected of issuing threats against black students.

University of Missouri Police say they arrested Hunter M. Park, who is white, early Wednesday for allegedly making threats against black students. Park, police say, is not a student at the university.

Reporting from Columbia, Mo., NPR's Adrian Florido said tensions were high on the campus last night. He told our Newscast unit that:

"The threats were posted on Yik Yak, an app that lets users remain anonymous. One warned students not to go to campus today.

"It spread quickly through social media, and soon, some black students were leaving their dorms out of fear, preferring to spend the night with friends off campus.

"In a tweet, the school's chancellor acknowledged the social media threats and said campus police had increased security. Later, a police spokesman said there was no immediate threat.

"On Twitter, though, many black students said they were too afraid to attend classes today. Some demanded all classes be canceled. Some professors did cancel their classes."

Early this morning, the university issued a fresh statement, saying the suspect was not arrested on campus and that the university was "operating on a regular schedule."

Police said that Park was being held in jail "in lieu of $4,500 bond."

"Safety is the university's top priority and we are working hard to assure that the campus remains safe while information is obtained and confirmed," the statement added.

Throughout the protests that led to the resignation of Chancellor R. Bowen Loftin and system President Tim Wolfe, black students complained that the university administration was ignoring these kinds of threats.

On Twitter, the Concerned Student 1950 movement said that these fresh threats were "validating our concerns."

Jonathan Butler, the graduate student who went on a hunger strike, posted what he purported to be a back-and-forth between a professor and a student.

Before the suspect was arrested, the student told the teacher that she did not feel safe coming to class. The professor allegedly responded that he would be in class and that "there will be an exam administered in our class."

Updated at 6:50 p.m. ET:

Published reports say the professor who made the statement has offered his resignation.

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