I looked through my brothers(15) computer and found out he sent a dick pic to someone but I feel guilty, advice?

my brother has anxiety and is a awkward person who has been bullied most of his life and he started talking to other teens during the summer who were lonely on the Internet like him (uses reddit and discord) and so he could talk to his friends who he doesn't see much during the summer. when he was out of his room and his computer was on I figured he had gotten a girlfriend recently since he makes it pretty obvious, but me and him are not not supposed to date until 16 but I wasn't going to tell our parents I just wanted to check to see if he was doing something stupid and I was right he sent a dick pic to his girlfriend that he was talking to on discord, but I closed discord and turned off the computer before reading the entire conversation, I want to confront him about it but I feel guilty, guilty I looked through his computer without him knowing, and I have a close relationship with my brother and don't want to ruin that, advice?