you, he, she, etc. started it

(someone) started it

Someone else began a fight, argument, dispute, etc., as opposed to oneself. Usually said in or associated with childish arguments or fights. A: "Stop it you two! I'm taking you both to the principal's office." B: "But she started it!"
See also: start

you, he, she, etc. ˈstarted it

(spoken, informal) you, he, she, etc. began a fight or an argument: ‘Stop fighting, you two!’ ‘He started it!’
See also: start