"Police then lit up the nearby highway to provide a safe landing point, but as they were doing this they heard a crash and the chopper was down."
The helicopter was taking the boy to hospital with a severe breathing disorder from his home just north of the township of Marlborough in the northern state of Queensland.
Queensland Emergency Services Minister Stephen Robertson said the helicopter pilot had radioed that he was running out of fuel shortly after taking-off.
"The pilot tried to land several times at the Marlborough school grounds but wasn't successful," Robertson said in a statement.
"Police then lit up the nearby highway to provide a safe landing point, but as they were doing this they heard a crash and the chopper was down."
The accident was the first fatal crash involving a Queensland Emergency Services helicopter since the service began flying 20 years ago.
The helicopter's pilot, a paramedic and an ambulance officer also died in the crash.
Community 'shock'
Rescue workers said visibility in the area at the time of the accident was practically nil.
"It was virtually zero ... very, very heavy in fog,"' fire service officer Trevor Kidd told ABC Radio.
Local Police Inspector John Larkin the small community of Marlborough was in deep shock at news of the accident.
''The rescue helicopter up here is one of the major lifelines for outlying communities,'' he said.
Capricorn Helicopter Rescue Service, which operated the crashed helicopter, is under contract to provide airborne medical transport in the region to Queensland's Emergency Services Department.
It deals with an average of four medical emergencies each week and officials say they have asked the state government to provide an interim helicopter so the service can continue.
A spokesman for the Queensland premier's office said an interim helicopter would be made available within two days.