Ambulance crews attended the incident in Haast on Wednesday evening, but were not able to resuscitate Samuel. Photo / FileA source told Stuff the boy had been using an outdoor shower, in which a gas bottle heated the water.
The boy was unconscious when his mother went to check on him - presumably having been overcome by the gas.
St Johns ambulance crews rushed to the scene but were unable to resuscitate him.
Constable Paul Gurney, of the Haast police unit, told Stuff the boy's death was a "tragedy for the family" as well as the town.
"It's not good when someone dies, especially when it's a 12-year-old. Haast St John did a sterling job to try and revive him but to no avail."
A police spokesperson said Samuel's death has been referred to the Coroner.
Police were making enquiries on the Coroner's behalf.