“Four weeks after the barbaric terrorist acts of October 7th, I have lost confidence that you and the university will do what is required,” Ackman wrote, describing the Cambridge campus as a place where Jewish students are concerned about the threat of physical violence against them.

A Harvard spokesperson pointed to the university’s prior comments over campus safety and community conduct but declined to directly address Ackman’s letter.

Tensions on campuses, including Harvard, Stanford, Columbia and the University of Pennsylvania, have surged since Hamas breached Israel’s border last month, killing 1,400 people and taking more than 200 hostages. Demonstrations have regularly been held against Israel’s bombardment of Gaza, which has led to the deaths of almost 9,500 people, according to the Gaza health ministry run by Hamas.

Antisemitic incidents including assaults, harassment and vandalism soared 400% across the US since Oct. 7, with 54 incidents reported on campuses, according to the Anti-Defamation League.

The protests have divided campuses over the limits of free speech and strained relations among students, faculty, alumni and donors. At Penn, alumnus Marc Rowan has called for its leaders to resign amid charges they’ve tolerated antisemitism on campus.

The reputational damage to Harvard, the oldest US college, began hours after the attack by Hamas, when more than 30 Harvard student groups posted a letter placing the responsibility solely on Israel. Hamas is deemed a terrorist organization by the US and European Union.

Former university president Larry Summers slammed the institution’s failure to condemn the groups.

Ackman, founder of investment firm Pershing Square Capital Management and a frequent contributor to social media, suggested that there should be employment consequences for those that signed the letter.

The threat of consequences to students for antisemitic actions became evident Thursday when a group of prominent law firms sent letters to the deans of more than 100 law schools, including Harvard, telling them to take an “unequivocal stance” against antisemitic harassment on their campuses. The firms, which include Sullivan & Cromwell and Cravath, Swain & Moore LLP, grew quickly from two dozen to more than 100.

Gay, who began the job as Harvard’s president on July 1, has issued multiple messages condemning the attacks and last week appointed a group of advisers to work with Harvard leadership on combating antisemitism. In an Oct. 27 speech at Harvard’s Hillel, she said she acknowledged grief, fear and anger among Jewish students and faculty.

But in his letter on X dated Nov. 4, Ackman was dismissive of her efforts and described the situation as “much worse” than he realized.

“Jewish students are being bullied, physically intimidated, spat on, and in several widely-disseminated videos of one such incident, physically assaulted.”

Ackman urged the immediate suspension of those involved in “harassing and allegedly physically assaulting” the student on Oct. 18, as well as disciplinary action against students who post antisemitic content on Slack message boards.

Ackman also took issue with students chanting ““Intifada! Intifada! Intifada! From the River to the Sea, Palestine Shall Be Free!”

The phrase has been widely interpreted as calling for the expulsion of Jews from Israel and the dismantling of the Jewish state.

Ackman charged that inaction by Harvard in confronting the problem created by a small group of students and faculty has “emboldened this antisemitic subset of the community to escalate their antisemitic actions.”

“As Harvard’s leader, your words and actions are followed closely,” Ackman wrote. “As a result, the steps you take to address antisemitism at Harvard will be recognized around the world, and can contribute greatly as an example to other institutions seeking to eliminate antisemitism in all of its forms.”