What does Judges 9:24 mean?

This happened so that the violence done to the seventy sons of Jerubbaal would be paid back, and so their blood would come back on Abimelech, who killed them, and on the leaders of Shechem, who helped him murder his brothers. Judges 9:24 - Modern Text Bible

(The conflict is God's way of bringing justice for the murder of Gideon's sons, holding both Abimelech and the Shechem leaders responsible.)