This is a developing story.

NEW YORK (JTA) — The Ethical Culture Fieldston School, an elite New York City prep school, has fired a teacher who posted tweets opposing Zionism.

JB Brager, who taught history at Fieldston, was fired Thursday, the Jewish Telegraphic Agency has learned. The termination comes after Brager, who is Jewish, posted multiple tweets disparaging Zionism amid a controversy over anti-Zionism and anti-Semitism at the school.

“ECFS does not comment on personnel matters,” the school said in a statement to JTA Thursday evening. “We can reaffirm, however, that the school does not tolerate hurtful, offensive, or exclusionary content or comments from any member of the community. Students, parents, employees and other members of our community all face consequences for misbehavior of this nature.”

JTA reached out to Brager for comment, but did not immediately hear back.

The controversy began in November when a speaker at the school, Kayum Ahmed, a lecturer at Columbia University Law School and a director at the Open Society Foundations, said that the Holocaust and Israel are examples of “victims becoming perpetrators,” according to a video obtained by the Washington Free Beacon. Tablet magazine reported that parents were “shaken and outraged” by the remark.