The head of the transport safety agency says a helicopter collision on the Gold Coast that killed four people could have been "far worse" as investigators begin piecing together what went wrong.
The two aircraft, operated by Sea World Helicopters, had been undertaking flights over the Broadwater at Southport when witnesses said the rotor blade of one chopper that had just taken off collided with the cockpit of another that appeared to be coming in to land.
Queensland Police Acting Inspector Mike Campbell said one of the helicopters crashed and of the seven people on board, four adults including 40-year-old pilot Ash Jenkinson were killed.
He said a 36-year-old woman from Glenmore Park in New South Wales and a 57-year-old and 65-year-old couple from the UK also died.
Thirty-three-year-old Winnie De Silva, her nine-year-old son Leon from Geelong and another 10-year-old child, from New South Wales, were critically injured and remain in hospital.
The other helicopter with a pilot and five passengers landed on a sand bank and all survived the incident, although the pilot and a passenger were injured.
Australian Transport Safety Bureau Chief Commissioner Angus Mitchell said investigators were at the scene and had begun collecting evidence.
He said witness accounts and camera footage of the incident would be valuable in the investigation.
"We're still determining the exact sequence of events but from the footage that we've seen and from the damage that we can witness on there, it does appear that the main rotor blade of the helicopter taking off has collided with the front cockpit of the descending helicopter on the left-hand side," he said.
"That in itself has led to the main rotor in the gearbox separating from that helicopter, which has meant that tragically it has then had no lift and has fallen heavily to the ground."
He said the second helicopter's landing on the sandbar has prevented further fatalities.
"Whilst it has been very tragic that four people have lost their lives and many families are mourning this morning, we could have had a far worse situation here and the fact that that one helicopters managed to land has been quite remarkable," he said.
Both helicopters have been removed from the sandbank and perishable evidence relating to the investigation was recovered last night.
Anyone who witnessed the incident or has footage has been asked to contact the agency.
Pilot and British citizens among the dead
Mr Jenkinson, who was a Sea World Helicopters pilot, died in the crash with friends paying tribute to him on social media.
Many spoke of Mr Jenkinson's generous spirit, including how in March last year he put together a team to help victims of the floods in northern NSW.
Andrew Taylor remembered his friend of six years as a "big guy with a big heart" and "someone you just naturally wanted to be around".
"He was a very good pilot, so for something like yesterday to happen sort of blows your mind a little bit."
He told the ABC Mr Jenkinson leaves behind a toddler son and a partner.
The British Foreign, Commonwealth and Development Office (FCDO) said it was providing assistance to the loved ones of the UK citizens.
"We are supporting the family of two British nationals who died in Australia and are in contact with the local authorities," the FCDO said in a statement.
The fact they had landed on a sandbank outside the Sea World resort made it difficult for emergency crews to access the crash scene, Queensland Police Service Acting Inspector Gary Worrell said.
Both aircraft had been operating out of a terminal next to the Sea World Marine Park, which was packed with holiday-makers. Passengers were taking flights over the Broadwater, which was also crowded with boats.
Witness feared for crowd
John Hunt, who witnessed the crash while visiting Sea World, said he feared one of the helicopters was going to crash on top of the crowd.
"We looked up and we heard a bang and we saw one helicopter had hit and had already started to crash,'' he said.
"The other helicopter hovered over the Jelly Fish building [in the park]. We thought he was going to crash on top of all the crowd, but the pilot was able to get out onto the sandbank, probably an extra 30 metres away from where it was."
Mr Hunt said the pilot who managed to land on the sand bank had saved many lives because the park was "choked with people".
He said he did not know what caused the crash, but that it was "pretty windy".
"They've got a big windsock near the helicopter area. The windsock was full of air," Mr Hunt said.
Steve Raschilla saw one of the planes "break into pieces".
"One of them from underneath, seemed like [it] came up and hit the bottom of the other one on top," he said.
"I don't know if they were both trying to land at the same time, [or] what they were trying to do."
Mr Raschilla, a nearby resident, said it was not unusual to see helicopters fly in the area, but it was odd seeing helicopters out in windy conditions.
Sea World Helicopters cooperating with investigations
Sea World Helicopters said on its website it was closed until further notice and "will refund all tickets purchased".
The company issued a statement on Monday expressing "shock and deepest sympathy" for those involved in the accident.
"We are cooperating with all the authorities including the Australian Transport Safety Bureau and the Queensland Police. As it is now a police investigation we cannot provide any further information at this stage," it said.
Eight patients were taken to Gold Coast University Hospital and one to the Queensland Children's Hospital in Brisbane, the Queensland Ambulance Service said.
Mr Hunt said Sea World staff, people on jet skis and recreational boaties had rushed to the scene of the crash "to try and help" after it happened.
"Those people will probably see some really horrific things today," he said.
Village Roadshow Theme Parks (VRTP), which runs the Sea World theme park, offered its "deepest condolences" to those impacted by the tragedy.
"While Sea World Helicopters is an independent professional operator, VRTP is working with emergency services and the authorities to provide every possible assistance," it said in a statement.
"We are providing support to our team members who have been emotionally affected by the tragedy."
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