The official said that the suspect had been arrested before, but apparently only for low-level offenses, including peddling. Vendors who said they knew the man, who has not been officially identified, said he ran errands and helped them haul their wares to storage for $5 a trip, and that he showed up on Tuesday with his head and beard shaved.

“I showed him The Post,” said Liz Willis, who runs a newsstand on the corner. “ ‘This looks like you,’ ” she said she told him. “He said, ‘That’s not me.’ ” She saw a detective lead him away a short while later. Another law enforcement official said the man did odd jobs for street peddlers, making roughly $40 a day.

The freelance photographer who took the pictures, R. Umar Abbasi, defended his actions in an interview. “I’m being unfairly beaten up in the press,” he said at his apartment in Greenwich Village on Tuesday, before leading a reporter to the 49th Street subway platform to re-enact what had happened.

Mr. Abbasi said he was wearing a 20-odd pound backpack of camera gear for an assignment, and was standing near the 47th Street entrance to the platform when he saw the man fall on the tracks. “Nobody helped,” he said. “People started running away.”

“I saw the lights in the distance,” signaling a subway’s approach, he said, so he started firing off flashes on the camera — 49 times in all, he said — as a means of warning the driver.

“I was not aiming to take a photograph of the man on the track,” he said, later adding that his arm was fully outstretched, the camera far from his face.

“If I had reached him in time, I would have pulled him up,” he said. At one point, the man said to have shoved Mr. Han came toward Mr. Abbasi, he said, so he backed up against a wall, still flashing his camera. He estimated the victim was on the tracks for 10 or 15 seconds before he was struck.