Australian police have charged a 19-year-old man with murder after a boy, aged 12, was fatally shot in the face and neck at a Sydney home last month.

Police were called to a unit in Sydney’s northwest on 21 September after reports of a shooting. The boy was rushed to hospital in a critical condition and died three days later.

Nine people at the home when the shooting happened were uninjured. Three men – all aged 18 – were arrested and two later released without charge.

The third man, Isaac Bechara, who has since turned 19, was initially charged with concealing a serious indictable offence and remanded in custody. On Tuesday, police charged him with murder.

Bechara did not apply for bail when he appeared in court on Wednesday.

In the immediate aftermath of the shooting, New South Wales (NSW) police ruled out links to organised crime but days later, investigators said they were looking at possible gangland connections.

“A number of individuals that were inside the unit at the time are well known to NSW Police and their association with organised crime is being considered by investigators,” said Supt Naomi Moore last month.

Moore added that some of the people who were present at the time of the shooting were “not currently co-operating with investigators” and that police were yet to recover the firearm.

Local media reported that the incident was a suspected accident, citing police sources, and that the boy’s father had paid tribute to his son on social media, posting a photo of the pair with the caption, “RIP my baby”.

When the boy’s death was announced, NSW Police Commissioner Mal Lanyon said any incident “where we lose a young life in those circumstances is tragic”.