What the hell did I do?

Time and time again I ask myself the question, "What in the hell did I do?" It is usually a cut and dry answer. Not this time. I don't know what I did. One moment I was partying with a couple friends having the time of my life. The next moment I have a bloody knife in my hands and I am covered with someone's blood. As I survey the scene, I notice I am in a dark creepy alleyway. But the most horrifying part of the scene is the body laying about 3 feet from me. It is the body of my best friend. Then I repeat to myself over and over again, "WHAT THE HELL HAVE I DONE?" And this time I can give no answer, because I don't know.