The woman got up from her seat, walked behind the man along the platform, mumbling to herself, witnesses told the police, before shoving him into the path of a No. 7 train just after 8 p.m. Witnesses said the victim did not appear to notice her.
The man, whom the police have not yet identified, was pushed with little time to avoid the hurtling train, or for others to come to his aid, said Paul J. Browne, the chief police spokesman. His body remained under the second car, which officers from the Emergency Services Unit planned to lift using specialist inflatable bags to recover his remains.
"We haven't determined whether it was random or if there was some connection yet," Browne said, "but there was nothing from what the witnesses could see to indicate that they knew each other and he did not, according to the witnesses, appear to realize that she was approaching."
The woman, whom the police described as Hispanic, in her early 20s and heavyset, fled and was being sought.
Outside the elevated station Thursday night, multiple police vehicles gathered, and local residents braved frigid conditions to huddle on corners and discuss the act of violence in their midst. Three police trucks sat lined up along the tracks, lights flashing against the backdrop of a string of white Christmas lights.
Investigators were unable to immediately determine much about the victim beyond his gender, Browne said.
Giovanni Briones, 44, the owner of the Oasis Restaurant on 40th Street and Queens Boulevard, said the police were able to obtain clear images of the suspect from his 24-hour cameras.
"She jumps from the stairs and she just runs," he said, describing the video he provided to detectives. He said he did not recognize the woman.
"I'm sure they're going to get her," he said. "There are a lot of sick people out there - mentally ill. It's very sad." Residents in the area were still shaken, he added, by an episode in the summer in which a man killed his wife and jumped from the tracks at the same subway stop.
In the restaurant, another woman anxiously described her husband, who she had not heard from, for a police officer. She was overjoyed when he called a few minutes later.
Briones said one of his regular customers was on the train. She told him later that "she felt a bump as the train ran over the man," he said.
The No. 7 line was shut down between Court Square and 61 Street-Woodside Avenue, Deirdre Parker, a spokeswoman for the Metropolitan Transit Authority, said late Thursday.
It is the second time this month that a man has been killed after being pushed onto the subway tracks. Ki-Suck Han, 58, of Queens, died under the Q train at the 49th Street and Seventh Avenue station in early December. Naeem Davis, 30, has been charged with second-degree murder in that case. A lawyer for Davis said his client had been trying to push Han away after an altercation.