A 33-year-old single mother allegedly committed suicide by consuming sleeping pills after she gave the same pills to her 55-year-old mother and six-year-old daughter at their Boral home, on the southern fringes of the city, on Tuesday night.

The woman died. Her mother and daughter have survived.

Police said the family was in distress because a man the victim had trusted defrauded her with false assurances of marriage and forced them to sell their flat, one of their few assets, for the money. Once he got the money, he allegedly refused to marry her — driving the woman to the drastic step.

The 38-year-old man, from Haridevpur, was arrested on Wednesday evening. He will be produced in court on Thursday.

An officer said a probe revealed that the 33-year-old woman had met this man four years ago through a matrimony site.

“The man had been promising marriage since then. According to the allegations, he had taken gold and money from the family on multiple occasions and was forcing the family to sell their flat through distress sale, so that he could take that money, too,” the officer said.

Officers said the family did not have any source of income and had allowed their ancestral property to be developed into an apartment block, in which they had taken a flat.

The woman who survived has lodged a police complaint on Wednesday blaming the man for allegedly cheating her daughter with the false promise of marriage and forcing the family to sell their flat at a low price for his financial benefits, police sources said.

Based on the complaint, officers of Bansdroni police station have arrested the man and started a case of cheating and abetment to suicide and common intention against him.

“According to the complainant, soon after they transferred the property title to the new owner, her daughter realised the man was going to take all the money but not keep his promise to marry her. The daughter decided to end her life and also fed her mother and the child sleeping pills,” said an officer.

The child vomited and her cries alerted neighbours, who broke into the house on Tuesday night and rushed all three to a hospital near Garia.