Abimelech lived at Arumah: and Zebul drove out Gaal and his brothers, that they should not dwell in Shechem.
The curse of Jotham that fire would come out of the bramble and burn Shechem surely was fulfilled with this brutal slaughter and destruction of the whole city of Shechem.  One wonders about the mother of Abimelech and all of her people.  We do not know whether or not they had moved to Arumah where they might have escaped this massacre.