Gaal the son of Ebed came with his brothers, and went over to Shechem; and the men of Shechem put their trust in him.
"Would this people were under my hand, then would I remove Abimelech"  (Judges 9:29).  The fatal flaw in this insurrection was that Zebal, Abimelech's deputy governor of Shechem, was present and reported the whole affair to Abimelech.