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INVERNESS, Ill. (WGN) — A suburban Illinois father allegedly poisoned his children before he died by suicide, killing his son and putting his daughter in critical condition, police say.

Inverness officers were called to a home in Inverness at around 4:20 p.m. Sunday for a well-being check.

Inside, a father and his son, 10-year-old Austin Chang, were found dead. The father has been identified as Woo Chang, 41.

The boy’s 6-year-old sister was located inside and transported to a hospital in critical condition. Police said the cause of death was carbon monoxide poisoning due to a generator.

Police met with the children’s mother, who told them the children did not return at the scheduled time with her estranged husband. She was the one who found her children inside the home.

Autopsies are scheduled for Monday.