NSW Police are treating the deaths of two 22-year-olds at a Western Sydney home on Saturday afternoon as a murder-suicide.

Just before 12:45pm, emergency services were called to a home in Tongariro Terrace in Bidwill after reports of a stabbing.

NSW Police found the woman outside the house with stab wounds from a knife to her chest, sides and back.

She was treated at the scene by paramedics before being taken in a critical condition to Westmead Hospital, where she later died.

The man was found inside the home with stab wounds to his chest, which police said were self-inflicted. He died at the scene.

NSW Police Detective Chief Inspector Paul Tickner said it was believed the pair had recently broken up and that may “have been the underlying cause” of the incident.

“It’s a tragic loss of life, they’re only 22 years old, they had their whole life in front of them and unfortunately both are lost to us,” he said.

He said the family members of the man were home during the attack and attempted to intervene.

“This has come out of the blue, so [the families] are all distraught,” the Detective Chief Inspector said.

NSW Police said it was not searching for anyone else in relation to the deaths.

A crime scene was established at the home.