The police summary of facts released to the Herald shows that Vaigafa had been drinking at a neighbour's house when he was confronted by his victim.
Vaigafa went into the kitchen and grabbed a large knife from a drawer, the summary says.
The woman tried to run away but Vaigafa followed her down a driveway.
"[Vaigafa] had the knife in his hand and started to stab at the victim's back and shoulders, striking her at least four times," the summary says.
The force of the blows bent the tip of the knife.
She ran across the road with Vaigafa still swinging the knife at her.
They both fell to the ground, with Vaigafa on top of the victim.
During a struggle over the knife, Vaigafa's little finger was almost severed.
Police arrived and the attacker got off the victim.
At the time the summary was written by a police detective, the full extent of the victim's injuries were not known.
"Doctors have confirmed the victim has four stab wounds on her shoulders and chest," the summary says.
After he was arrested, Vaigafa admitted that he "wanted to kill" the victim.
Justice Cameron Mander remanded him in custody to be sentenced on October 2.
The judge called for a pre-sentence report and victim impact statements. A cultural report will also be prepared.