A father and his 10-year-old son have died after the dad allegedly used a carbon monoxide generator to intentionally poison himself and his children.
Woo Chang, 41, and his son Austin both died from the lethal fumes.
His six-year-old daughter Jeslyn only survived the gassing when the children's mother came to her estranged husband's home because they were late home from a custody visit.
The incident reportedly took place in the suburban village of Inverness, in the US state of Illinois, last Sunday.
The mother reportedly went to her ex-partner's home after he failed to bring the children back following scheduled visitation hours.
The woman immediately alerted Inverness police after seeing their unconscious bodies upon arriving at around 4.20pm.
Investigation details showed that Chang intentionally put a generator inside the home.
Inverness Police Chief Bob Haas who witnessed the sight said it was a tragedy.
"It's never a pleasant situation. I've been doing this for over 40 years, but it's a sad thing."
Scheduled autopsies should reveal the victims' cause of death.
Whiteley Elementary School, where 10-year-old Austin was a student, said the community is reeling.
"The District is simply heartsick, and in both shock and mourning over the tragic loss of one of our students.
"It goes without saying that this is a devastating loss for all of us here in District 15, especially as we look to the remainder of the school year where the child's absence will be felt by classmates and staff."
A GoFundMe campaign has been started to help the Chang family with funeral costs and medical bills.
An update on the crowdfunding page from September 16 says six-year-old Jeslyn is "doing great" but remains in hospital.
"She had an echo [echocardiogram] that looked good. She is opening her eyes and tracking. Listening to some commands. She is even recognising faces and staring lovingly at her mama," the update read.
"They are taking her breathing tube out today as she is breathing on her own. Keep the prayers coming, they are working."
Do you have a story tip? Email: email@example.com.