Should I tell my fraternity bro. that I caught another frat bro "touching" him while he was ped out?

After a huge party in my fraternity, I took one of my fraternity brothers back to his room because he was wasted. When I went back to check on him several hours later, I walked in on another frat bro "touching" him while he was ped out. He had his pants down and...well...let's just say it wasn't exactly mouth to "mouth." Should I tell the victim what I saw? I'm really torn about what to do.