Hunter Park is pictured in this undated booking photo provided by Boone County Sheriff's Department in Missouri. Park, was in custody on November 11, 2015, for making online threats to shoot black students at the University of Missouri following racial protests that prompted the school's president and chancellor to step down this week, campus police said. REUTERS/Boone County Sheriff's Department/Handout via Reuters

(Reuters) University of Missouri police arrested a 19-year-old white man on Wednesday on suspicion of making threats on social media to shoot black people, just two days after the school’s president and chancellor stepped down following protests over their handling of reports of racial abuse on campus.

Tensions at the university’s main Columbia, Missouri campus are still running high after the resignations on Monday, with a greater-than-usual police presence and several students leaving the area saying they felt unsafe.

Police arrested suspect Hunter M. Park of Rolla, Missouri, which is about 95 miles (150 km) south of Columbia, at about 1:50 a.m. local time. He was not a student, according to police.

Police said the suspect’s threats had circulated on social media, including Yik Yak, where an anonymous post tagged ‘Columbia’ late on Tuesday read: “I’m going to stand my ground tomorrow and shoot every black person I see.”

“We’re waiting for you at the parking lots,” said another post. “We will kill you.”

Yik Yak is an anonymous social media application that allows users to create and view posts within a five-mile radius. Yik Yak spokeswoman Hilary McQuaide said the company had worked with police to identify Park, saying the company may do so “when a post poses a risk of imminent harm.”

Park was arrested under Missouri law which prohibits communication of a life-endangering threat to at least 10 people. He was transported to Columbia and is being held at the Boone County Jail on $4,500 bond.

On Twitter on Wednesday morning, the hashtag #PrayForMizzou was trending in the United States and many postings highlighted the anonymous threat on Yik Yak. ‘Mizzou’ is the colloquial name for the University of Missouri.

Despite a heavier-than-normal police presence on campus, a few students decided to return home because they felt unsafe, students told Reuters.

University authorities said classes were operating on schedule. However, some professors, acting individually, canceled classes. Other teachers gave students the option of not attending classes.

Bradley Smith, a graduate instructor of English, took to Facebook on Tuesday night to cancel his class.

“By holding class at our regular time, I would be forcing my students who do and probably should feel threatened, to implicitly disobey me in order to protect their lives by not attending my class,” he wrote.

At one point on Wednesday, there were reports that members of the Ku Klux Klan were on campus, but Missouri Students Association president Payton Head later said on Facebook that was incorrect.

Some students expressed frustration and anger at the school for not officially canceling classes on Wednesday and downplaying the threat, students told Reuters.

On other U.S. campuses, peaceful marches or walkouts have been held this week, or are planned, over what some demonstrators see as soft handling of reports of racial abuse on campuses.

Soon after Missouri president Tim Wolfe announced he would step down on Monday, a crowd of more than 1,000 gathered peacefully at the Afro-American Cultural Center at Yale University in New Haven, Connecticut, for a “March of Resilience,” in solidarity with Missouri.

The crowd sang and chanted for an end to racism on campus. The issue has been in focus at Yale after a fraternity turned away black guests at a Halloween party, saying, according to reports at the time, that only white women would be admitted.

A walkout is also planned at Ithaca College, a private school in upstate New York.

A student group called People of Color at Ithaca College announced on its Facebook page it was planning an on-campus ‘Solidarity Walk Out’ at 1:30 p.m. on Wednesday and demanded the resignation of Ithaca president Tom Rochon.

Students at Smith College, a women’s private school in Massachusetts, plan a similar walkout for midday on Wednesday.