Four-year-old Justin Gore had been staying with relatives in Joliet, Illinois because his parents were going on a Caribbean vacation.
A relative had looked in on the boy at 5am before driving his parents to the airport. Justin and his younger sister were left in the care of other adults.
The child, who is autistic according to the Chicago Sun-Times, was reported missing by family around 10.30am. No one was sure how he was able to get out of the house.
Minutes later, a 911 call said that a boy had been found in an above-ground pool, two blocks away at the Miletta family home. The pool had stairs but no gate.
After attempts at CPR, the boy was taken to Provena St Joseph Medical Center where he was pronounced dead shortly before midday.
The Miletta family went to stay at a hotel after the tragic death, being too upset to remain at their home.
Although the families did not know each other, Justin’s great-grandfather went to console the family.
He told the Chicago Tribune: ‘I understand his daughter found [the boy], and she was just hysterical. I had to explain to them that it wasn’t their fault.’
The following day, Mr Miletta planned to tear down the pool and was driving to a hardware store when he suffered a fatal heart attack at 9am, three blocks from his house.
He lost control of his SUV and ran across a front yard, hitting the porch before the car rolled over. No one else was injured.
Will County coroner’s office ruled Miletta died of ‘multiple cardiac conditions’.