Caught my friend jacking off?!?!

Went to my friend house today to do his little sisters hair, got there and everything was fine. He went into his room because he said "u girly girls are boring to death", and then smiled and went into his room. I was half way done with his sister hair when I realized I didn't have my phone, so I headed towards his room to ask can I use his phone but when I opened his door I caught him looking at a p*rn site while jacking him self off, I immediately shut the door so his sister didn't see him, then I turned and faced his door so I couldn't see nothing and asked him to cut it off and to stop. Then he says "hold on 1 second, I'm almost finished". Is that normal, and why did he act like he didn't care that I was standing there... Should I be worried?
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Last time I was at his house me and a friend kept "bugging" him by knocking and he told us "for now on this house is like your house so don't bother to knock", so of coarse I didn't knock.
Caught my friend jacking off?!?!
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