NEW YORK (AP) —  A passageway connecting New York City’s Port Authority bus terminal and the Times Square subway station is back in use the day after a bomb went off there.

Security remains tight citywide on Tuesday.

An NYPD official says the man accused of detonating the bomb was not previously known to authorities. Deputy Commissioner for Counterterrorism and Intelligence John Miller said on CBS “This Morning” that Akayed Ullah wasn’t on police or FBI’s radar before the Monday morning bomb in Times Square.

He says it’s getting harder and harder to defend against such acts because would-be terrorists are going online to read propaganda without speaking with any larger group.