When a father and son were arrested this summer in Ontario over an alleged terrorist plot, U.S. authorities say the news spooked a 20-year-old Pakistani national and Canadian resident named Muhammad Shahzeb Khan.

They say Khan used encrypted messaging to warn that because of the arrests “here in Toronto,” there was a need to “lay low” on his own alleged plans: killing as many Jewish people as possible in New York around the Oct. 7 anniversary of Hamas’ attack on Israel.

But the person receiving the message wasn’t an ally of Khan’s — they were an undercover American agent.

U.S. authorities and the RCMP on Friday announced that Khan had been arrested in Ormstown, Que., on Wednesday over his alleged plot to attack a Jewish centre in Brooklyn with guns and knives in the name of the Islamic State.

They said Khan, also known as Shahzeb Jadoon, was arrested on his way to New York to carry out his plans.

United States Attorney General Merrick Garland said Khan was alleged to have had the goal of “slaughtering, in the name of ISIS, as many Jewish people as possible.”

He said Khan was arrested thanks to “quick action” by Canadian law enforcement.

In a complaint filed in New York’s southern district the day of Khan’s arrest, FBI special agent Khajae Hester said Khan used encrypted messaging apps to communicate with undercover agents posing as willing participants in the plot, asking them to buy “automatic and semi-automatic weapons.”

The complaint says that since last November, Khan “repeatedly and explicitly expressed his support for ISIS and his desire to carry out terrorist attacks in support of ISIS.”

The complaint says Khan boasted the mass shooting would be “the largest attack on US soil since 9/11.”

It said he would face one count of attempting to provide material support and resources to a terrorist organization.

The RCMP said it conducted an investigation into Khan in partnership with the FBI and “as his actions escalated, at no point in time was Khan an immediate threat prior to his arrest.”

It says Khan faces three charges in Canada: attempting to leave Canada to commit an offence for a terrorist group, participating in activities of a terrorist group and conspiracy to commit an offence by violating U.S. immigration law or attempting to enter the U.S. unlawfully.

Mounties said Khan was set to appear in the Superior Court of Justice in Montreal on Sept. 13, and that the U.S. would seek extradition.

The U.S. complaint against Khan alleges he told the officers of his desire to create “a real off-line cell” of the Islamic State, directing them to obtain assault rifles and ammunition and “some good hunting (knives) so we can slit their throats.”

Oct. 7 was chosen as the date for the attack because there would likely be protests, the complaint says, while the Oct. 11 Yom Kippur holy day was also considered.

There was a hitch when the RCMP announced on July 31 that Ahmed Eldidi and son Mostafa Eldidi had been arrested and charged with terror-related offences in Toronto, allegedly prompting Khan to warn the officers the next day to stay off social media.

But the complaint says the undercover officers told Khan last month they had secured weapons and, at 5:40 a.m. on Wednesday, he allegedly got in a vehicle in Toronto and set off for Napanee, Ont., picking up “additional passengers on the way.”

In Nepanee, the complaint says, they switched to a second car and drove to Montreal, where Khan and an “unidentified female” changed vehicles again, with another person at the wheel, the complaint says.

At 2:54 p.m., about 19 kilometres from the U.S. border, the vehicle was stopped by police and Khan was arrested.

“The defendant was allegedly determined to kill Jewish people here in the United States, nearly one year after Hamas’ horrific attack on Israel,” FBI director Christopher Wray said in a statement.

RCMP Commissioner Mike Duheme said “there is no place for such ideological and hate-motivated crime in Canada.”

“Violent extremism in all its forms is on the rise around the world and Canada is not immune. This planned antisemitic attack against Jewish people in the U.S. is deplorable,” Deheme’s statement said.

This report by The Canadian Press was first published Sept. 6, 2024.

Darryl Greer, The Canadian Press