A three-year-old girl has been found dead with a gunshot wound to her neck at a home in Sydney's west.

Emergency services were called to the Lalor Park home just after 8pm on Sunday where they discovered the devastating scene.

A man inside the house reportedly screamed “she’s dead ... she’s shot herself’’ as concerned neighbours rushed to the scene.

As police spoke to a hysterical woman outside the Danny Road home, neighbours watched the "chaos" unfold.

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A visibly distraught man was filmed sitting in the gutter with his head in his hands as police made their way into the home. Source: 7 News

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The woman was heard yelling "I hate you, I hate you" as she was treated by paramedics. Source: 7 News

A visibly distraught man was filmed sitting in the gutter with his head in his hands as police made their way into the home.

Mel Toilalo was just down the road when she heard what sounded like a car crash outside her front door.

“I ran outside ... I saw a man on the floor, he was screaming ‘she is dead’ or ‘she has shot herself’,’’ Ms Toilalo told News Corp.

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Emergency services were called to the Lalor Park home just after 8pm on Sunday where they discovered the devastating scene. Source: 7 News

“She was screaming it was his fault because he had a gun in the house.’’

Other children inside the home were believed to be her brothers and sisters, police have confirmed they are all between the ages of three and eight years old.

Detectives from Quakers Hill Local Area Command remain at the scene on Monday morning and are speaking with the family.