Emergency services were called to a Lalor Park home on Danny Road in Sydney's west at 8pm on Sunday where a three-year-old girl was found with a fatal gunshot wound to her neck.
NSW Police media said in a statement that detectives from Quakers Hill are continuing to investigate the circumstances surrounding the incident.
NSW Police has not said anyone has been charged or arrested in relation to the death.
ABC News reported the girl's mother was extremely distressed and was taken away in an ambulance screaming "I hate you" and "not my baby girl", and that the girl's three siblings were at home at the time of the shooting.
UPDATE: NSW Police have charged the 43-year-old father of the child with firearm offences and contravening an apprehended violence order.
NSW Police said in a press conference on Monday morning that he will appear in court later today.
They have reiterated that people should keep firearms safe and stored in accordance with the law.