The incident took place on Saturday afternoon on the New York subway when the suspect was walking between train-car doors and asking passengers for money, according to US media reports.
The young mother, who wanted to remain anonymous for fear of being targeted again, was holding her baby in a harness when the beggar was coming towards her.
She says she asked the woman begging to “please stay 6 feet away”, to which the woman responded by stepping on the young mother’s foot, reported the New York Post. The 21-year-old said she pushed the female beggar away to protect the baby and that is when the latter turned and “started punching the baby multiple times”.
“She didn’t even hit me” and fled when the train reached the West 116th Street station, the young mother said, telling the Post: “Nobody tried to help me. I yelled, ‘Someone help me, take the baby!’ No one did nothing to help.”
The mother said there were plenty of people on the train at the time and every seat was occupied.
The mother said her son, who has asthma, suffered minor injuries on his face and ear and is so traumatised that “he won’t let me touch him by the face.”
“I will never forget her face. She looked evil,” the mother said.
The New York Police Department (NYPD) said it was looking for the attacker, who is described as being in her forties, with a neck tattoo and buzzcut.
Considered one of the busiest train systems in the world, every day millions use the New York subway for their daily commute.
The NYPD recently beefed up security on the subway, with hundreds of additional police officers added to patrols, after several stabbing incidents.