What would you do if you heard your brother jerking off?

Let's say you have a 16 year old son. One day after you came home you heard moaning and sighing coming from his room. Your brother breathes louder then he moans with pleasure and shouts oh yes! ( he's using a toy) he has no idea you are there because he always gets out of school 2 hours before you come home. What would you do/ say?
What would you do if you heard your brother jerking off?
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