Police had been treating the incident as a possible murder-suicide attempt but the case will now be closed, Montreal police Constable Danny Richer said.
The woman died of her injuries from the near-drowning Wednesday at 1:30 p.m. Her 4-year-old son died of his injuries Monday afternoon.
The woman’s two-month-old son, however, is doing much better and has been released from hospital and returned to his relatives’ care.
The trio had entered the frigid water in the Bassin des Pecheurs that bisects the Parc Nature de l'Îsle de la Visitation, said a witness.
A witness said the woman appeared to have had been attached with something "like a scarf" to her 4-year-old boy - and had the infant at her side - when he saw the trio in the water in the Rivičre des Prairies by the waterfront park.
Police said the family is of Turkish nationality and lives in Montreal North.
The events happened in the late afternoon. The father had reportedly notified police that his wife and children were missing before they were pulled from the water.