Three people have died and a man is in police custody following an incident at a home in Sydney’s southwest.

NSW police arrived at the house in Rosemeadow on Sunday at 1.30am after reports of a disturbance.

Officers found a 64-year-old man suffering serious head injuries, along with the bodies of a woman in her 60s and a man in his 20s.

The injured man received medical treatment from NSW ambulance paramedics and Liverpool hospital, but later died.

As of Sunday morning, the bodies were yet to be formally identified.

Police said the victims “were assaulted by a man known to them”.

Police arrested a 32-year-old man, who was taken to Campbelltown police station for questioning.

Officers had set up a crime scene and were preparing a report for the coroner. Police said the incident was being treated as domestic violence-related.

More details soon …