It's believed 10-year-old Bentley, who was neurodiverse, was playing with friends in Mooroopna in northern Victoria when he became trapped in the car boot, suffering cardiac arrest on Sunday when temperatures peaked at 35C.
His aunt Lainey set up a Go Fund Me page to help his family cover funeral costs, with $5600 raised by Tuesday towards its $20,000 goal.
"In a tragic end to a game of hide and seek, our world stopped," Lainey said in a statement on behalf of the boy's family.
"As a family, our hearts are broken as we try to find some sense in a place that no longer feels whole."
Bentley's death came just two weeks after the loss of his grandmother.
Another aunty, Steph Sutton, shared her grief on social media, describing Bentley as a "shining star".
"The loss of Bentley has been nothing short of an absolute tragedy," she posted.
Police say they aren't treating the boy's death as suspicious but investigators are still probing the circumstances and a report will be prepared for the coroner.
28°C