Students at the University of Pennsylvania and other colleges around the nation walked out of their classrooms at precisely 2:15 p.m. on Thursday to demonstrate against racist messages that circulated around the West Philadelphia campus last week.

"We all refuse to attend universities or live in a country where people threaten our safety and silence us," organizers behind the Facebook event #StandWithPenn wrote on the page. "We need your help to make this possible."

The event was coordinated by Students Organizing for Unity and Liberation and Black Graduate and Professional Student Assembly.

The action, in which students planned to wear all black, comes less than a week after black freshmen at the university were added to a GroupMe group app called "N— Lynching," which included a calendar with days marked for "daily lynching."

The man believed to be responsible for the incident was a student at the University of Oklahoma, who had been offered admission into Penn, and had access to the app. The reaction was a mix of fear and anger among Penn's student body.

One student told the website Billy Penn that the rise of racial slurs around campus was the result of Donald Trump winning the presidential election. Those kinds of incidents, according to the student, are "definitely an outright response to Trump winning."

Penn is Trump's alma mater; he graduated from the Wharton Business School in 1968. But a majority of the student body was vocal about its dislike for the Republican during the protracted campaign. In October, staff at the school newspaper, the Daily Pennsylvanian, published a joint editorial with students from Wellesley College's Wellesley News, that endorsed Hillary Clinton for president. Clinton graduated from Wellesley College in Massachusetts.

Penn students who participated in the walkout Thursday met at the College Green in the middle of campus, where black student leaders read a statement in a show of solidarity.