BBC says:
They also confirmed that the man who remained in hospital was the former partner of a woman who was visiting the family at the house.
Sounds like she was possibly the target and maybe not the woman who died. I do wonder if the 'former partner' had left him and gone to stay with her friend? We know that women are in the most danger when they try to leave.
Either way and whatever part these various men played, how absolutely awful. Yet again women and children dying due to male violence.