The father of a young girl wrapped his arms around his limping daughter and hugged her.

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Police and emergency crews worked tirelessly for hours under extremely difficult circumstances and later several could be seen comforting each other.

Those were just some brief moments of love among chaos after two young girls and two young boys fell to their deaths at a school fun day at Hillcrest Primary School on Thursday.

The school was holding an end-of-year celebration when about 10am a gust of wind threw a jumping castle and several inflatable 'zorb' balls 10 metres in the air.

Police say a number of Grade 5/6 students were on the castle at the time.

Five children have since died, and another four suffered critical or serious injuries and were taken to hospital in ambulances and the rescue helicopter.

A fundraiser started in the wake of news filtering through about the fatal tragedy, which brought in $100,000 within seven hours.

Police on Thursday afternoon said there were a number of witnesses to the event, and that a more exact number would be determined by an investigation.

Traumatised parents had earlier that morning rushed to the school to collect their kids after they heard about the incident, not knowing if they were okay.

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Frantic parents and grandparents were desperately asking if anyone had seen their children.

Parents, neighbours, children and school staff were crying with shock and horror as they watched emergency services flood into the school.

They watched on as ambulance officers treated several injured children behind a blue tarp erected near a tree at the bottom of a hilly embankment.

A shocked witness who lives across from the school said he had seen several children on the ground as he watched the terrible events unfold from his front balcony.

He said his wife had heard a "big bang," which drew their attention to the school oval.

"There was a strong gust of wind out of the blue, and I could see the jumping castle going up," neighbour Bob Smith said.

Mr Smith said he saw the inflatable jumping castle set up for what was to be a lovely day of entertainment and fun.

He said it was awful to think what had happened.

The shaken mother of a grade three pupil said she first heard about the incident while she was Christmas shopping at the Kmart.

"My father-in-law called me, and I swore at the top of my lungs," she said.

"You think the worst. It's just horrendous. You don't expect this to happen in your own neighbourhood.

"You see these things on the news happening elsewhere when things go bad."

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She said her son's class had been waiting for their turn on the jumping castle just before the tragedy.

Her son said his class was meant to be the first to go on the attraction but were held back until grades five and six had their go on the jumping castle.

The mother said she was thankful her son was safe but felt terrible for the parents of children on the jumping castle when the wind struck.

At the confronting scene, a sombre Western District Commander Debbie Williams gave an update to the media to confirm that two children had died at that point, encouraging people to reach out for support.

"This is a very tragic event, and our thoughts are with the families and the wider school community and also our first responders," she said.

"There is no doubt that this has been a very confronting and distressing scene.

"Support and counselling is being made available to the families and the school community, along with the first responders."

At the end of the long, sad day, Police Commissioner Darren Hine confirmed there had been four deaths and five injured.

Another child died later in the night, bringing the toll up to five.

"On a day where these children were meant to be celebrating their last day at primary school, instead we are all mourning their loss," Commissioner Darren Hine said.

He said police and WorkSafe investigations would continue into the amount of children on the castle at the time, and how it had been secured down.

Premier Peter Gutwein described the entire incident as "utterly devastating and heartbreaking".

"I know that this is a strong community, I know that they will support each other through this," he said.

Devonport mayor Annette Rockliff said the tragedy was difficult to process and would "undoubtably rock the close-knit community for a long time".

"Our hearts are broken - there are no words to be honest," Cr Rockliff said.

"What should have been a day full of fun and celebration for the last day of the school year, has ended in an unimaginable way."

Cr Rockliff said the council would look for practical ways to help the Hillcrest Primary community into the future.

"While we can't take away the anguish this part of our community is currently going through, we will be there in any way that we can," Cr Rockliff said.

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"I encourage us all to be there for each other, to offer support to your friends, your family, your neighbours, who are having a hard time processing the enormity of this situation.

"And to those who have been affected in any way, our hearts are with you."

She said the council would fly the Australian flag at half-mast as a sign of mourning with its community.

Devonport Uniting Church at 12 Forbes Street will be open from 10am-2pm on Thursday as a space to pray, share, light a candle and think of the families, friends, staff and emergency services affected.

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