Why did I wake up feeling guilty?

I had this dream that me and my sister were shopping in this clothing store. This guy walks up to us and asks us to come with him, so we do. He leads us to this door that lead to some stairs that go down into a underground clothing store. I remember being very happy because he had said he wanted to take pictures of us. So were picking out clothes and for some odd reason I break into song and the guy is playing the piano and singing along with me. Then these strange men come and the guy leaves to talk to them. I start to get uneasy. Somehow I figure out that he wants to trick me and my sister and hold us hostage. So I grab my sister and we run back upstairs but the stairs have all these twists and turns now so it takes us a good 3 minutes to get back up there. By that time the guy knows we have fled so he's after us. We make it back upstairs but my sister trips and falls and the guy drags her back down stairs. I was scared so I said I wasn't going to get her. Then I woke up