It is becoming a familiar riddle for residents of New Jersey: how did a resident become radicalised to the point where he launched a terrorist attack in New York City?
For the second time in a little over a year, the state’s Muslim population is on edge.
On Tuesday night, police and FBI agents moved through Paterson, cordoning off a residential address and a mosque, as well as searching a rental car depot. They were hunting for clues in the vehicle attack that killed 8 people and injured 11 on a bike path in Manhattan.
Details are gradually emerging about Sayfullo Saipov, 29, who was apprehended after being shot in the abdomen.
Law enforcement officers said they had found a note in the vehicle declaring allegiance to ISIL even as people living close to Saipov tried to comprehend what had happened.
A man who identified himself as Saipov's neighbour told NJ Advance Media that the suspect was a frequent guest at his home, since moving to the area with his wife and two children a few months earlier.
Last year, Ahmad Khan Rahimi, from Elizabeth in New Jersey, launched an attack in Manhattan’s Chelsea neighbourhood. At least 29 people were injured when a pipe bomb detonated in a dumpster.
Law enforcement officials would be looking into any possible link, said Mitchell Silber, former director of intelligence analysis at the NYPD.
“New Jersey has some significant middle Eastern and Muslim populations and the fear from the NYPD perspective is that individuals aren’t going to attack anything in New Jersey, they would come to New York,” he said.
He added that all the indications now pointed the attacker being motivated by terrorism.
Several news outlets reported that handwritten notes in Arabic were found by the truck. A senior law enforcement source told The National that a note inside the car referred to ISIL.
The details and the nature of the attack mirror instructions issued to Isis adherents in the West.
The November issue of the movement's magazine Rumiyah offered details instructions for mounting an attack with a vehicle, including how best to ensure Isis gets the credit.
“An example of such would be simply writing on dozens of sheets of paper ‘The Islamic State will remain!’ or ‘I am a soldier of the Islamic State!’ prior, and launching them from the vehicle’s window during the execution of the attack,” it says.
Officials believe Saipov first lived in Tampa Bay, Florida, after arriving with a Green Card from Uzbekistan.
There he met Kobiljon Matkarov, 37, who told the New York Post he had bonded with Saipov over their shared heritage.
“He is very good guy, he is very friendly… he is like little brother… he look at me like big brother,” he said by telephone from his home in Ohio.
He added that Saipov had worked as an Uber driver, and had taken him and his family to Kennedy Airport in New York when he travelled back to Uzbekistan during the summer.