June 17th, 2025

Quebec man who killed his young twins displayed domestic violence signs: coroner

By Canadian Press on June 17, 2025.

MONTREAL — A Quebec coroner is recommending improved domestic violence training for the province’s police officers.

André Cantin’s recommendation follows his investigation into a man who killed his three-year-old twin sons shortly after he was arrested for allegedly harassing his ex-partner.

Cantin says in his report that Ian Lamontagne displayed a pattern of coercive control toward the mother of the children before he killed the young boys and then died by suicide.

Lamontagne had tracked her movements, showed up at her home, and repeatedly called and texted her before the murders.

He was arrested outside the woman’s residence in August 2023 for criminal harassment, and released on a promise to appear in court at a later date.

About two days later he used helium to suffocate three-year-olds Antoine and Tristan Lamontagne at his home in Notre-Dame-des-Prairies, Que., north of Montreal.

Cantin says the province should ensure that current and future police officers and family mediators are given more training on how to recognize potentially dangerous situations within families.

This report by The Canadian Press was first published June 17, 2025.

The Canadian Press

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