A Glenmore woman was stabbed to death in the early hours of Sunday when a suspect gained entry into her home.
Two of her relatives were also stabbed and are in critical condition in hospital.
Garrith Jamieson, the director of ALS paramedics, said they responded to the call for help just after 3.30 am.
"Paramedics arrived on scene to a horrific scene. A family had been attacked inside their house by an alleged suspect. Paramedics found three patients with multiple stab wounds. Immediately more ambulances and advanced life support paramedics were dispatched to assist."
He said a female believed to be in her forties had sustained multiple fatal stab wounds to her body.
"There was nothing paramedics could do for her and she was declared deceased on the scene. Two men, believed to be father and son, had multiple stab wounds to their bodies."
Jamieson said both were in critical condition and required multiple advanced life support techniques to stabilise them on the scene.
"They were rushed to a nearby hospital for the required urgent care. At this stage the events leading up to the attack are unknown. However, SAPS were in attendance and will be investigating further."