NEW YORK — A man accused of planning to firebomb the home of a prominent Palestinian activist has been arrested following a weekslong undercover operation led by the New York City Police Department, officials said Friday.

The target of the plot was Nerdeen Kiswani, who frequently leads protests in New York against Israel and the war in Gaza through the organization Within Our Lifetime.

Kiswani, 31, said law enforcement officials informed her late Thursday that they had disrupted “a threat on my life that was about to take place.”

Federal authorities said they arrested Alexander Heifler on Thursday at his home in Hoboken, New Jersey, as he was assembling Molotov cocktails that he planned to throw at Kiswani’s home. For weeks, he had discussed the plot with an undercover NYPD detective who had infiltrated a group chat used by Heifler, according to a police department spokesperson.

An official who was briefed on the investigation said Heifler, 26, identified as a member of the JDL 613 Brotherhood, a New Jersey-based group founded in 2024 that describes its membership as “Jewish warriors” fighting back against rising antisemitism.

A website for the group says they are inspired by the original Jewish Defense League, a group linked to numerous bombings and attempted assassinations of Arab American political activists in the 1970s and 1980s.

Heifler planned to flee to Israel following the attack, according to the official, who requested anonymity because they were not authorized to discuss the details of an ongoing investigation.

An email inquiry sent to the JDL 613 was not returned.

Kiswani, who lives in Brooklyn with her infant son and husband, said the plot would not deter her continued activism.

“I feel very blessed that they were able to thwart this, but it’s something that is a constant possibility for people who speak up on behalf of Palestine,” she said.

Heifler was charged in a criminal complaint with separate counts of making and possessing destructive devices, which each carry a maximum penalty of 10 years in prison. A message left with his attorney was not returned. He made an initial appearance in New Jersey federal court on Friday afternoon.

“Let me be clear: We will not tolerate violent extremism in our city,” New York City Mayor Zohran Mamdani said in a statement. “No one should face violence for their political beliefs or their advocacy. I am relieved that Nerdeen is safe.”

According to a court filing written by an FBI agent, Heifler spoke on a video call in February with a group that included an undercover detective about his interest in training for “self-defense” and wanting space where he could throw Molotov cocktails.

The next day, he met with the undercover detective in person and discussed his plan to use them against Kiswani and flee the country, according to the complaint. “We have (Kiswani’s) address,” Heifler allegedly told the undercover. “So it’s like that, that would be easier if you’d be more comfortable with that.”

Heifler and the undercover detective drove to Kiswani’s residence on March 4 to “conduct surveillance” and discussed making a dozen Molotov cocktails to throw at her home and two cars parked outside, complaint said.

On Thursday, the undercover detective and Heifler met at Heifler’s Hoboken residence, where he had assembled components to make the Molotov cocktails, including a large bottle of Everclear, a highly flammable alcohol, the complaint said. Law enforcement officers then executed a search warrant at the residence and recovered the eight Molotov cocktails, the complaint said.

Kiswani co-founded the group Within Our Lifetime, which frequently organizes protests against Israel that draw hundreds of participants and often end in arrests. The group’s calls to “abolish Zionism” and support for “all forms of struggle,” including violence, has drawn fierce criticism. Kiswani denies that her criticism of Israel amounts to antisemitism.

Kiswani has been a frequent target of online vitriol. Earlier this year, U.S. Rep. Randy Fine, a Florida Republican, sparked backlash after writing in a social media post that “the choice between dogs and Muslims is not a difficult one.” The post was a response to a message Kiswani shared about dog owners, which she said was a light joke.

“That hate against Palestinians has been bolstered by public officials, by Zionist organizations, who are never held accountable,” she said. “This is the inevitable result of that.”

The operation was carried out by the Racially and Ethnically Motivated Extremism unit within the NYPD’s counterterrorism bureau, a police spokesperson said.

“This is exactly how our intelligence and counterterrorism operation is designed to work — a sophisticated apparatus built to detect danger early and prevent violence before it reaches our streets,” Police Commissioner Jessica Tisch said.