The New York Police on Saturday detained a woman, who allegedly pushed a 46-year-old Indian origin man to death in front of a subway train in New York, sending shock waves among millions of commuters who use the city’s expansive transit system daily.

The 31-year-old woman made statements implicating herself in the crime, NYPD said. The police did not release the suspect’s name until they formally charge her.

Sunando Sen was killed after the woman shoved him on to the tracks of an oncoming train in a Queens subway station on Thursday night.

The incident was the second time in December that a person was pushed on to the subway tracks by a fellow commuter.

Sen had opened a small copying and printing business this year in the city’s Upper West Side.

He was hit by the first car of the train and his body was pinned under the second car before the 11-car train came to a stop.

The condition of Sen’s body had made it difficult for the police to identify him and investigators used his phone and a medicine bottle he was carrying for his identification.

Police said his family in India has been notified.

According to Sen’s roommates, he was not married and his parents were dead.

A.R. Suman, one of the four roommates with whom Sen had shared a small apartment, described him as a “very educated person and quite nice”.

“It is unbelievable. He never had a problem with anyone,” Suman said in a New York Times report.

There was no video at the subway station and the New York Police Department released a surveillance video from near the station showing the suspect running away from the scene.

New York Police Department chief spokesman Paul Browne said according to witnesses, the woman had been following Sen closely and was mumbling to herself.

Mr. Suman said Sen had toiled hard to save money to open his printing business and hardly took a day off from work.

“I asked him why do you work seven days a week?” Mr. Suman said. “He told me, ‘I cannot hire someone because business is not good’’’.

Sen’s roommates said they could not think of any reason as to why the woman pushed him onto the tracks.

They said Sen had suffered a heart attack about nine months ago and was taking medication. “This guy was so quiet, so gentle, so nice,” another of Sen’s roommate M.D. Khan, a taxi driver, said.

“It’s so broken, my heart,” he said adding Sen enjoyed watching funny clips on YouTube and would listen to classical Indian music.

Meanwhile, witnesses said Sen was looking out over the tracks and the woman was sitting on a wooden bench near the wall behind him.

He had his back towards her and was not aware that she was approaching him. As the train pulled into the tracks, the woman got up from the bench and pushed Sen over.

Mr. Browne said according to witnesses, the attack happened so quickly that Sen had little time to react and neither could the bystanders do anything to save him.

“There’s one witness who was sitting on the bench with the woman, the perpetrator here,” he said. “And there are other witnesses who were on the platform itself. So we’re in the process of gathering information“.

The shocking incident comes just weeks after 58-year-old Ki-suck Han was pushed in front of a subway train in Times Square by 30-year-old homeless man Naeem Davis.

New York Mayor Michael Bloomberg said such attacks were exceedingly rare and there is little that can be done to prevent such incidents.

“I don’t know that there is a way to prevent things,” Mr. Bloomberg said. “There is always going to be somebody, a deranged person”. He said such incidents were tragic for the families of the victims.

“You can say it’s only two out of the three or four million people who ride the subway every day, but two is two too many,” he told reporters.

“We do live in a world where our subway platforms are open, and that’s not going to change,” he added.

Through posters pasted on the subway walls, New York authorities have tried to caution commuters about safety on subway platforms.

They adviced people to stand away from the edge of the platform and that they should never cross the tracks to get to the other side of the station.

The trains and the platform are not separated by any barriers.

In 2011, 146 people were struck by New York subway trains, of which 47 died, according to the Metropolitan Transportation Authority.

The city’s subway system is more than a 100 years old and is one of the world’s busiest, ferrying millions of commuters daily.