Charges filed againston Wednesday depict the Uzbek immigrant as a disciple of ISIS propaganda.
"It appears from what we know now, and this could change, that he was radicalized after he came to the United States," said John Miller, NYPD deputy commissioner of intelligence and counterterrorism and a former CBS News senior correspondent.
The authorities are asking key questions of the suspect's motive and whether he acted alone in the deadly attack thatand injured a dozen others.
"When you capture a live terrorist, you have the ability to question that person and you're able to glean a lot about those things: Were they part of a larger network? Is this something bigger? Were they acting alone? But you can also go deeper into those questions about what brought you to this point. And there are former defendants in cases like this where we've learned a lot about the arc of their radicalization, and what we're seeing today is, in the United States, a great deal of that is just done online," Miller said.
Asked how the "arc" of radicalization can be broken, Miller replied, "we have no effective counter message today."
"This is something that has vexed us since 9/11 when the U.S. government started looking at this, and it is a prescription that is very hard for the government to deliver. This is something that we have been in discussion with the larger Muslim community about how to do, and we're not there yet," Miller said.
On Tuesday President Trump called the suspect an "animal" and called for the repeal of the Diversity Visa Lottery program that allowed him to enter the U.S. The president also claimed that "chain migration" had allowed Saipov to bring 23 people into the country. Miller, however, said he knew "nothing" about the claim and said it "would be a stretch" to suggest that any of the others who came into the U.S. through that visa program or with Saipov had some relation to terror plots.
Miller said the Joint Terrorism Task Force and the FBI areto figure out: "Is this inspired? He just got all this off the internet? Was it enabled? Was he actually communicating with ISIS officials over encrypted channels or was this directed? Was this part of a plan?"
"At this point we don't see anything that leads us to believe there's anyone else involved, but I caution we're a day or two into this," Miller said.