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NEW YORK — Akayed Ullah, the 27-year-old Bangladeshi man accused of detonating a home-made device in a pedestrian subway tunnel in the heart of New York on a busy Monday morning, has been charged with terror and weapons counts.

Authorities said federal charges are expected soon.

Here’s what we know so far about the explosion and failed attack:

The location

The blast detonated around 7:20 a.m. in an underground walkway connecting two subway lines beneath the Port Authority Bus Terminal, near Times Square, which accommodates 220,000 passenger trips a day.

The suspect was first spotted on a security camera as he began to climb the subway station stairs to the 18th Avenue F. train platform in Brooklyn at 6:25 a.m., according to one law enforcement official with direct knowledge of the investigation.

He then switched to the A train at Jay St./MetroTech stop in Brooklyn before exiting the train at the Port Authority Bus Terminal stop in Manhattan, the same law enforcement official says.

On grainy surveillance footage, commuters are seen walking through a tunnel when a burst of smoke erupts into the hallway, quickly filling it. Commuters flinch and take cover. When the smoke clears, a man can be seen lying on the ground in the hallway.

The suspect

Ullah is currently hospitalized at Bellevue Hospital, where he is being treated for lacerations and burns to his hands and abdomen, New York City Fire Department Commissioner Daniel Nigro said. He is said to be seriously injured.

On Tuesday, Bangladesh counterterrorism officers began questioning his wife and relatives in his native country.

Relatives and police said Ullah last visited Bangladesh in September to see his wife and newborn son. He left both behind when he returned to the United States.

Ullah arrived in the United States in 2011 and the Department of Homeland Security said he is a lawful permanent resident of the U.S. who was living in Brooklyn. He came to the U.S. on a visa issued to him based on a family connection to a U.S. citizen.

Law enforcement officials familiar with the investigation said Ullah had looked at Islamic State group propaganda online and told investigators he was retaliating against U.S. military aggression, but had no direct contact with the group. The people spoke on the condition of anonymity because they weren’t authorized to speak publicly about the blast.

Ullah’s uncle, Abdul Ahad, said the suspect mostly remained inside a small apartment in Dhaka’s Hazribagh area when he recently visited Bangladesh.

“He went out of his residence to offer prayers at a nearby mosque,” Ahad told The Associated Press.

He said Ullah arrived in Bangladesh on Sept. 8 and returned to New York on Oct. 22.

“He stayed with his wife and 6-month-old baby boy,” he said, adding that Ullah was a quiet person who rarely socialized.

Ahad said Ullah also returned to Bangladesh two years ago to get married and stayed then for about three months.

Abdul Mannan, an official involved in the investigation, said Ullah appeared to have no criminal record in Bangladesh and was not a known member of any militant group.

The government said in a statement that “Bangladesh is committed to its declared policy of ‘zero tolerance’ against terrorism, and condemns terrorism and violent extremism in all forms or manifestations anywhere in the world, including Monday morning’s incident in New York City.”

Bangladesh, a Muslim-majority country governed by largely secular laws, has struggled with a rise in radical Islam in recent years.

The bomb

Ullah had at least two devices, a law enforcement source with knowledge of the investigation tells CNN.

Only one detonated — a foot-long pipe that contained black powder, a battery, wiring, nails and screws. It was attached to Ullah with Velcro and zip ties. Investigators did not elaborate on the second device.

The suspect made the bomb last week at his apartment in Brooklyn, according to an official. New York Gov. Andrew Cuomo said it was an amateur, “effectively low-tech device.”

The explosive chemical ignited, but the pipe itself did not explode, lessening its impact, Cuomo told CNN’s Wolf Blitzer.

“Fortunately for us, the bomb partially detonated,” he said. “He did detonate it, but it did not fully have the effect that he was hoping for.”

The victims

Five people were treated for minor injuries in area hospitals.

“Mount Sinai Health System received and treated five patients with minor injuries as a result of the explosion today at Port Authority; four at Mount Sinai West and one at Mount Sinai Queens,” a statement from the hospital group said.

“All were in stable condition and were release today. We are working closely with officials in law enforcement in the wake of this event.”

The response

Ullah was apprehended by Port Authority police officers shortly after the blast. Four of the officers involved in the apprehension and arrest of the suspect have been named as Sean Gallagher, Drew Preston, John Collins and Anthony Manfredini.

“Today, four courageous Port Authority police officers risked their lives confronting an armed terrorist to protect others from harm,” Port Authority Police Benevolent Association President Paul Nunziato said in a statement.

“I am so thankful there was no loss of life and I could not be prouder of our Port Authority police officers, their actions and dedication to their sworn duty.”

New York Mayor Bill de Blasio called the incident an “attempted terrorist attack,” while Police Commissioner James O’Neill called it a “terror-related incident.”

All subways and trains are running as scheduled, except the passageway where the incident occurred. Some exits and transfers may be blocked so passengers may be affected.

Gov. Cuomo praised the courage of the authorities, first responders and the city’s residents.

“I am deeply grateful to the first responders and security personnel who kept people safe after today’s attack and brought the suspect into custody,” he said.

“Despite this morning’s terrible incident, New Yorkers went about their lives unafraid, undeterred and more united than ever before. We will not allow this to disrupt us.”

He added that he was directing the World Trade Center spire to be lit in red, white and blue “as a symbol of our essential values of freedom and democracy.”

US President Donald Trump said Monday that an attempted terrorist attack in New York bolsters the need for his preferred immigration policies, which the White House says would have prevented the suspect from entering the country.