New York just had its deadliest terror attack since 9/11 — that’s “stunning,” says one expert

"Speaking to Mic on Wednesday, Brian Nussbaum, a former intelligence analyst and an assistant professor at the University of Albany, agreed that it is “very challenging” to gauge just how effective counterterrorism efforts are. Still, he said, there are indicators — one of which may in fact be the method used in Tuesday’s deadly attack."