The New York Police Department (NYPD) and the FBI arrested a member of a pro-Israel terror group, preventing what they said was a plot to assassinate a pro-Palestinian leader, according to media reports on Friday.

Alexander Heifler, 26, was charged in federal court with making and possessing Molotov cocktails that investigators said he was planning to use in the assassination attempt. But the criminal complaint did not specify a motive for the planned attack.

Authorities said Heifler was taken into custody at his home in the neighboring state of New Jersey, after detectives and federal agents searched his residence and found eight Molotov cocktails.

Police identified Heifler as a member of a branch of the Jewish Defense League, a pro-Israel group designated by the FBI as a terror organization. An undercover sting revealed that Heifler was planning an assassination attempt of New York's most well-known pro-Palestinian activist Nerdeen Kiswani, according to court documents.​​​​​​​

Investigators said Heifler had been planning the attack since at least February, when he discussed building and using Molotov cocktails for "self-defense" on a group video call that included an undercover detective.

According to the criminal complaint, the undercover detective met Heifler in person the next day and then two more times in the weeks that followed, including Thursday, when they built the eight Molotov cocktails together in Heifler’s home. He was arrested shortly thereafter.

Investigators said Heifler planned to use the explosive devices to target Kiswani, 31, the co-founder of the pro-Palestinian group Within Our Lifetime.

While making the weapons, detectives said Heifler told them he planned to throw some of the Molotov cocktails at cars and at least one directly into Kiswani’s home.

Heifler is being held without bond until his next court appearance. If convicted, he could face up to 20 years in prison. (AA)