"The defendant is accused of committing what is every subway commuter's worst nightmare -– being suddenly and senselessly pushed into the path of an oncoming train," Brown said.
The fatality was the second such incident in New York City this month. On Dec. 3, a man was killed when he was pushed onto the tracks in front of an oncoming train in Manhattan.
Menendez was seen talking to herself while seated on a bench at the 40th Street-Lowery Street station and was also observed pacing on the platform and muttering to herself. Sen was on the subway platform as the train approached, and Menendez allegedly pushed him from behind into the path of the oncoming train, according to the district attorney.
Witnesses said Sen didn't appear to notice his attacker, according to police. He was struck by the first of the 11-car train, and his body was pinned under the front of the second car as the train came to a stop.
Sen was a native of India who lived in Queens and had a printing business in New York City. He had no family in New York, according to police.
The suspect fled down two separate staircases to the street. Detectives had a surveillance video of the suspect running from the scene, police said.
The 40th Street-Lowery Street station is just six stops east of midtown Manhattan. Its narrow eastbound platform, elevated two stories above the street, is packed at rush-hour with exiting commuters forced to slowly funnel down stairwells past riders waiting to board trains.
In the Manhattan incident, at the Times Square station, Naeem Davis, 30, was charged with second-degree murder in the death of 58-year-old Ki-Suck Han, according to the Associated Press. Davis said he was coaxed into shoving Han onto the tracks by voices in his head he couldn't control, the AP said, citing the New York Post.
"It's sometimes in the back of peoples' minds because of the incident preceding this one, but there's no indication that it is related in any way or inspired it," Paul Browne, a police department spokesman, said of the death.
The NYPD announced earlier this week that there were 414 murders in New York City through Dec. 23, a 19 percent decrease from last year and fewer than the previous low of 471 reached in 2009. Barring a sudden spike in violence in the last week of the year, 2012 will mark the lowest murder total since comparable records began in 1963, Browne said. There were 2,262 murders in 1990, according to data posted on the NYPD's website.
Yesterday, New York Mayor Michael R. Bloomberg said in a statement that 2012 also saw the fewest number of shootings on record, with 1,353 compared with a previous low of 1,420 in 2009. Shootings have decreased by 8.5 percent so far this year compared to 2011 and 14.5 percent since 2001, Bloomberg said. The mayor is majority owner of Bloomberg LP, parent of Bloomberg News.
The No. 7 train extends from Times Square in Manhattan into Queens, terminating in the neighborhood of Flushing, east of LaGuardia airport. Police suspended service at the 40th Street station through the night while the investigation proceeded, reopening it to the public before the morning rush-hour.
Adam Lisberg, a spokesman for the Metropolitan Transportation Authority, said yesterday there isn't much the agency can do beyond warning people to stay away from the tracks on platforms. He said barriers between platforms and trains used in some transit systems, such as those used on platforms serving the AirTrain between the Jamaica area of Queens and John F. Kennedy International Airport, aren't suitable for the subway.
The subway system uses several different trains with doors in different positions so there's no uniform way to place the gates, and the cost would be prohibitive, he said.
"If we lived in a world of completely available unlimited dollars there may be a way to" prevent such incidents, said Joseph Lhota, the MTA chairman. "I don't think this is something that can be solved by spending more money in the subway system."
Lhota said that he encourages "all New Yorkers to stand back from the edge of the platform."
Editors: David E. Rovella, Michael Hytha
To contact the reporters on this story: David McLaughlin in New York at dmclaughlin9bloomberg.net; Joel Rosenblatt in San Francisco at jrosenblattbloomberg.net; Henry Goldman in New York at hgoldmanbloomberg.net
To contact the editor responsible for this story: Michael Hytha at mhythabloomberg.net