New York City Police Commissioner Ray Kelly was heckled off the stage at Brown University on Tuesday by critics angry over the NYPD’s stop-and-frisk policy.

Kelly, who had been scheduled to give a lecture on “Proactive Policing in America’s Biggest City” at the Ivy League college in Providence, R.I., was forced to cut his remarks short when dozens of students and activists protested prior to the afternoon lecture.

“Racism is not for debate,” one protester yelled, according to the New York Post.

Officials at Brown asked the protesters to reserve their comments until a question-and-answer session with Kelly, but the hall was cleared when the shouts did not end.

A federal judge recently ruled the department's stop-and-frisk policy violated the civil rights of minorities. The city is appealing the decision.

“We want you to stop stopping and frisking people!” another critic said, according to the Post.

Brown University President Christina Paxson later said the conduct was “indefensible” in a statement released following the incident.

“The conduct of disruptive members of the audience is indefensible and an affront both to civil democratic society and to the university’s core values of dialogue and the free exchange of views,” Paxson’s statement read.

Some students had earlier petitioned the university to cancel Kelly’s lecture, but when the school went ahead with the event, “we decided to cancel it for them,” Jenny Li, a Brown student who helped organize the protest, told the New York Post.

The Associated Press contributed to this report.