A five-year-old boy was playing with his sister in a bedroom when he was hit by a bullet fired into their southwest Sydney home.
The single shot was fired at the Lurnea home on Morison Drive about 9pm on Monday, hitting the boy in his hip.
The boy's parent didn't call an ambulance but instead drove five kilometres to Liverpool Hospital where staff alerted police.
"He suffered a gunshot wound while playing with his sister in the bedroom of their home," Superintendent Peter Gillam told reporters on Tuesday.
"I think they (his parents) heard a noise, they heard the child yell out ... and they've taken him straight to hospital."
The boy's sister was not hurt and police don't yet know the motive behind the shooting.
"We are currently talking to the parents, trying to establish what happened last night ... (if there is) any motive for what occurred," Supt Gillam said.
"We are not in a position to say whether this was targeted or random."
The boy is now in Westmead Children's Hospital in a stable condition and detectives hope to speak with him and his sister as soon as possible.
The family car has been forensically examined and the house was cordoned off for several hours while police investigated the crime scene.
Supt Gillam said officers had canvassed the area and talked to neighbours.
Investigators will look at CCTV footage too.
"We are throwing all the resources we can on to this investigation," Supt Gillam said.