Charles Ellicott Commentary Genesis 34:27

"The sons of Jacob came upon the slain, and plundered the city, because they had defiled their sister." — Genesis 34:27 (ASV)

The sons of Jacob. —After slaying Hamor and Shechem, the two brothers took Dinah and went out. It was after this that Jacob’s sons generally—though not without exceptions, for several of them were still very young—joined in seizing the spoil.