The incident occurred at around 2 pm during change of duty of RPF personnel at the busy station, the police official said.
The woman and child were waiting at Dum Dum metro station in the northern part of the city when the rifle of a constable went off. A bullet from the rifle hit a wall, richocheted and then injured them, he said.
The woman and her child were taken to a nearby hospital for treatment.
The reason for the rifle going off is being investigated, the official added.
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