What was my brother trying to do?

A year ago, I came home from school and my brother was acting nice to me and told me he had a surprise for me, which was really unlike him. He said it was in our basement and I could only see it when my parents left. I thought maybe he built something for me, so I was really excited. So I waited in my room, but then he came in and told me I should wear my pajamas, which I didn't understand. I said sure though, because I didn't care. Then, he came back and told me not to tell my parents what he showed me after he did, which kind of worried me. So i went to our basement to investigate, and I saw my brother had set up a bed, which made me think he was going to sexually assault me. I got scared and ran to tell my mom, who got very upset. I took her downstairs only to find the bed gone and my brother running upstairs. I was crying and worried and told my mom to talk to my brother. When she confronted him, he said he only wanted to show me a song he made and was to shy to tell anyone else, and thought he could trust me. I asked for evidence, but he said he deleted everything off the computer and it was gone. From then on, I've never trusted my brother and I always wondered what he was trying to do to me. Was he going to sexually hurt me or was it all for a good reason? Please, I'm scared to be with him and I need answers!