(NewsNation) — The Israel-Hamas war has sparked tensions and a rise of antisemitism on college campuses across the country, according to concerned students who say it’s become dangerous.

Jewish advocacy group The Anti-Defamation League reported that antisemitic incidents were up by about 400% in the two weeks following the Oct. 7 attack compared with the same period last year.

“This is not a spontaneous reaction that normal people have,” Oren Segal, vice president of ADL’s Center on Extremism, said during an appearance on “Elizabeth Vargas Reports.” “It speaks to the fact that some of this antisemitism and support for terror is deeply seated, not only in our public discussion, certainly online.”

A Cornell University junior accused of posting violently threatening statements against Jewish people on campus was held without bail after his first appearance in federal court Wednesday.

Patrick Dai, from the Rochester, New York, suburb of Pittsford, is charged with posting threats to kill or injure another using interstate communications. The graphic, anonymous messages posted this weekend on a Greek life forum rattled Jewish students on the Ithaca campus in Central New York.

“While we take some measure of relief in knowing that the alleged author of the vile antisemitic posts that threatened our Jewish community is in custody, it was disturbing to learn that he was a Cornell student,” Cornell President Martha E. Pollack said in a message Wednesday to the university community.

The incident isn’t isolated to Cornell.

Jewish students at Cooper Union College in New York City had to lock themselves inside a New York City library last week as anti-Israel protesters blocked the doors, according to multiple reports.

Video posted on social media showed the students in the library as a crowd of protesters pounded on the doors.

At Columbia University, a Jewish student was reportedly beaten after confronting a woman who was tearing down hostage posters. After a protest at Binghamton University, a student went viral in an online video for saying, “If Hamas is worse than ISIS, then Israel is worse than Nazi Germany.”

“We’re hearing from parents, people around the world that are just shocked that places that one would think one would go for an education for open debate, a civilized sort of discussion, are afraid because their classmates are often sharing ideas that legitimize violence,” Segal added. “That support the notion that Jews ought to be targeted.”

The Associated Press and NewsNation’s Tom Palmer contributed to this report.