this is used to describe when somebody does or says something that upsets another person or many people. It is used when telling someone else what you or someone else did. or as an answer when someone tells you what they or someone else did for example Person A: I told John that I dislike his Girlfriend. It really put the cat among the pigeons or as an answer when someone tells you what they or someone else did Person A: I told John that I dislike his Girlfriend. Person B: Wow I bet that put the cat among the pigeons

Sorry, I have found real description - to do or say something that causes trouble and makes a lot of people angry or worried. Tell them all they've got to work on Saturday. That should set the cat among the pigeons.

Maybe, when one man find himself in the vague environment.