NEW YORK (CBSNewYork/AP) — A witness described hearing a “boom” Monday after police said a man detonated a crude improvised device near the Port Authority Bus Terminal during morning rush.

It happened around 7:19 a.m. in an underground walkway between Times Square and the bus terminal subway stations in the area of 42nd Street between 7th and 8th avenues.

Christina Bethea was starting off her week rushing to work when she said the device exploded about 50 feet from her.

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“To me it sounded more like a loud gunshot, like ‘boom’ and it was over. Then smoke came and I ran upstairs. I don’t know what happened after that,” she told 1010 WINS’ Glenn Schuck. “When you hear ‘boom,’ smoke, that means get the hell out of there. That’s what I did.”

The 29-year-old from Yonkers, who was unhurt in the blast but shaken, decided not to go to work as a security guard and instead will spend time with friends in Harlem to calm her nerves.

The explosion triggered a massive response by police and firefighters both above and below ground, tangling subway and bus service.

“What are people thinking? You got crazy people walking around,” a man named Justin told WCBS 880’s Alex Silverman.

The attempted attack caused chaos and confusion for commuters trying to make their way to work.

Elrana Peralta, a customer service worker for Greyhound, said she works in the Port Authority terminal complex near where the blast happened, but didn’t hear the explosion.

“All we could hear was the chaos,” she said. “We could hear people yelling, ‘Get out! Get out! Get out!'”

John Miles, 28, from Vermont, was waiting for a bus to Massachusetts. He also didn’t hear the blast, but saw police react.

“I didn’t know what was going on. Officers were running around. I was freaking out,” he said. There was an announcement that people should take their bags and leave. “They didn’t incite panic. It was fairly orderly.”

“We walked to the job, but it was barricaded and they’re not letting anybody through,” said Jessica Carrion who works near the site of the explosion. “It’s scary. You could be anywhere. You could be strolling.”

“I give the NYPD great credit. I’ve never seen such a response in my life,” said commuter Shirley Beyah.

Beyah, acommuter from Orange County, New York, said she’s not familiar with the city subways but still, she wasn’t stressed for even one second when she was asked to turn around and walk back to Grand Central.

“We all walked here together. We got redirected to which trains to take and I’m telling you they really made us feel as though we were not going to die or have a hard time. Everyone just wanted to get away. No one wants to die on their way to work,” she said.

At Penn Station, there were a few disruptions with people standing around waiting and glad to be out of harm’s way.

“It’s unfortunate. I mean luckily no one was hurt but on the same token doing these things because you’re upset in your personal life or your personal beliefs it doesn’t change anything,” said Justin Thomas, a native of Brooklyn now living in Phildalephia.

At least three people were hurt in the explosion that Police Commissioner James O’Neill called “terror-related.”

Speaking at a news conference, O’Neill identified the suspect as 27-year-old Akayed Ullah.

Police said he had a crude improvised device attached to his body using Velcro and zip ties and said video shows him walking down the passageway when the device exploded.

O’Neill said by the time officers arrived, they found Ullah with burns and wounds to his body. He was taken into custody and transported the hospital.

Police asked anyone with information about the incident to call the Terror Hotline at 888-NYC-SAFE.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)