What happened during the attack? 

The explosion came in a passageway that connects the Times Square and Port Authority subway stations at around 7:20am US Eastern Time, setting off panic among the crowds of commuters who use the terminal and the connecting trains. The Port Authority, the world’s busiest bus depot, sits atop a sprawling, multi-line station.

A video released on Twitter shows a puff of smoke erupting amid a stream of commuters.

The New York Times reported Monday afternoon that Ullah told investigators he had chosen that particular location because of its Christmas decorations (paywall).

John Miller, NYPD’s deputy commissioner of intelligence and counterterrorism, said the device was based on a pipe bomb and was “affixed to his person with a combination of velcro and zip ties.”

Officials said it was unclear whether Ullah intentionally set off the device at that particular location, or whether it may have detonated on its own.

What do we know about suspect Akayed Ullah?

Ullah, originally from Bangladesh, had most recently been living in Brooklyn. He was, at least at one point, certified to drive a for-hire vehicle in the city, officials said.

In a statement to CNN, Allan. J Fromberg, spokesman for the city’s taxi and limousine commission, said Ullah held a for-hire vehicle driver’s license from 2012 to 2015, but was not licensed to drive an official yellow taxi.

“As taxi and for-hire vehicle drivers are independent contractors and not employees, I have no way of knowing whether he drove for any particular base, or whether he simply got the license but didn’t drive at all,” Fromberg said. “That said, since he held an FHV license, if in fact he did drive, we do know that it could not have been a yellow taxi.”

Shortly after the attack took place, police descended on at least three south Brooklyn addresses connected to the suspect or his relatives. Ullah came to the US with his parents and siblings in February 2011 on an immigrant visa, and had since become a permanent US resident, CBS News reported.

While there is no evidence that Ullah had any contact with ISIS or other extremist groups, he told investigators he had been inspired by the group’s online propaganda, a senior official told NBC.

Are there other threats to NYC at this time?

More than 230,000 commuters per day travel through the Port Authority terminal where the attempted bombing took place. Shortly after the attack, police evacuated the nearby subways. By 10 am, most transit service had resumed, although subways were still bypassing the Times Square-42nd street stop.

De Blasio said there are no other known credible threats to the city at this time.

“The terrorists will not win,” he said. “We’re going to keep being New Yorkers. Let’s get back to work.”

More than 3,000 officers patrol New York City’s sprawling transit system each day to guard against the terror threat that remains a menace for commuters around the world. In April, 15 people were killed after a suicide bomber hit the metro in St. Petersburg, Russia. Officials identified the prime suspect as a 22-year-old from Kyrgyzstan named Akbarzhon Jalilov.

In September, an attack on a London train injured 29 (paywall) when a bomb concealed in a bucket exploded during rush hour.

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