Neighbour's heroic act after father allegedly lit house on fire with his children inside - as heartbreaking sight is spotted in the front yard

A man has been praised for saving the lives of four children after their father allegedly set their home on fire, killing three of their siblings in Sydney's west.

Emergency services, including at least 20 firefighters and six fire trucks, rushed to Freeman Street at Lalor Park at 1am on Sunday following reports a home was ablaze. 

The man alleged to be responsible was Dean Heasman, 29, who was in a decade-long de-facto relationship with 29-year-old Stacey Gammage. 

Heasman is alleged to have lit the house on fire while Ms Gammage and her seven children were inside.  

Two boys, aged three and six, were taken to Westmead Hospital in a critical condition, but they died a short time later.

Fire and Rescue NSW extinguished the fire before the body of a third child, believed to be a 10-month-old girl, was found.

Neighbour Jarrod Hawkins rushed to the burning home just minutes after it was engulfed in flames and helped save four children inside. 

Details of his heroism emerged as a heartbreaking sight was spotted at the front of the house following the blaze: a lone baby walker seen on the grass with colourful toys in stark contrast to the burnt home.

Without hesitation, Mr Hawkins ran into the house and helped pull a nine-year-old girl and three boys aged, 11, seven and four, to safety. 

'I heard some stuff outside at 1am but by the time I came outside emergency was here - I couldn't do anything,' Mr Hawkins told Daily Mail Australia on Sunday. 

The young father said his daughter was friends with the nine-year-old girl and added that one of the boys had autism. 

He described the children as 'unreal' and said Ms Gammage and Heasman appeared to be happy.

His partner told Daily Mail Australia she was proud of him for running to the home and trying to help. 

'He did what anyone would do. He heard the sirens and he ran over,' she said. 

'I'm so proud of him. It's what you'd hope someone would do for your kids. I don't know what he heard when he got to the house and I can't imagine.' 

Another neighbour, Damien Dubois, said all three rooms at the front of the house were alight, with the surviving children placed on the other side of the road. 

'They had seven kids. I had the four kids and they were cold so we picked them up and took them into the back room,' Mr Dubois said. 

'I was trying to console them. The two younger kids weren't saying anything so I picked them up and took them out of the way of all this trauma.'

Mr Dubois said he was approached by the eldest child who had burns on both his arms, and told him 'he (Heasman) tried to kill me, I nearly died'.

He added both Mr Hawkins and the police were screaming at Heasman to 'get out, get out' of the burning home.

Blacktown Police Acting Superintendent Jason Pietruszka praised the actions of the first responders as 'quite heroic'.  

'The first responders were quite heroic in what they did, trying to gain access to a property that was well on fire,' he said.  

Mr Pietruszka explained Mr Hawkins assisted at the scene and his actions 'saved further lives from being lost'. 

The four children pulled from the burning house were treated at the scene before being taken to Westmead Hospital in a stable condition.   

Ms Gammage was taken to hospital for smoke inhalation while Heasman was arrested and taken to hospital under police guard. 

Heasman suffered serious burns and smoke inhalation from the fire and was placed in an induced coma in the intensive care unit. 

During a press conference on Sunday, police alleged Heasman hindered the efforts of first responders, police and neighbours to gain access to the home and to save the children. 

'Those actions were intentional in keeping responders and neighbouring out of the property with the intention of keeping the kids inside the property,' Homicide Squad detective superintendent Danny Doherty said. 

Neighbours who rushed to the scene and desperately tried to save the children from the burning home were allegedly fought off by Heasman.

Sources claim the father allegedly tried to drag the children back inside as rescuers attempted to pull them to safety. 

Heasman allegedly wanted to keep himself, the children and their mother inside the home. 

It is understood witnesses heard Heasman yelling something like 'let me die here' while the fire burned.  

Grim pictures have emerged in the wake of the blaze, with the fire completely destroying the property from the inside out. 

The front section of the house was blackened, with the bricks outside stained from where the flames blasted through the windows.

Outside window frames were scorched by the blaze, with the flames even licking the gutters on the roof.  

The home's front door appeared burnt off its hinges, while power cables leading to the house also appeared to have been burnt off by the fire.

It is understood the home was a housing commission property, where Ms Gammage lived along with Heasman and the seven children.

Mr Doherty said police were treating the fire as a domestic-related multiple homicide. 

'At this stage it does appear the 28-year-old is responsible for multiple deaths of young lives that have been tragically taken away,' Mr Doherty said. 

'We're alleging the 28-year-old man took actions to prevent the young people inside being rescued.' 

The State Crime Command Homicide squad along with the Arson squad have launched an investigation into the exact circumstances that caused the fire. 

Police are also using a specially trained accelerant dog to determine how the fire spread so fast.

The cause of the fire is not yet known and a report will be prepared for the coroner.