Police were searching on Wednesday for a man who pushed an 11-year-old boy between two subway cars on a moving No. 4 train last week.
The suspect was play-fighting with his brother as the train moved through Manhattan about 3:20 p.m. on Oct. 5 when they turned on the boy, a police source said.
The suspect pulled the boy into the area between the cars, picked him up and shook him, police said, threatening to throw him off the train.
The boy then bumped his head, police said, before a 26-year-old woman intervened and pulled him back into the train.
The woman and boy got off the train at the 14th Street/Union Square station, while the suspect stayed on the train, police said.
It was not immediately clear why the suspect targeted the boy but they did not appear to know each other, police said.