What causes a person to twitch like this?

I'm becoming obsessed with the desire to tear someone to shred. Just a random person. Or lots of random people. My goal has become to be the person with the most kills, that's over three hundred (in case you didn't know). I am constantly thinking of where the nearest knife is or how hard I'd have to hit someone with an object and how many times.to kill them. I don't care if it's my mom or someone I've never seen or hear of in my life. I'm sure it's just a phase or something and will be over eventually, but there are times, when I'm in private that I can't control it anymore and I twitch a little bit from the baldest. It's all about power and ual arousal for me when I think about it. To see the person cringe, shrink away, plead, scream, fight, and do whatever they can, but to have me just smile and rip them apart, cause them the most misery they've ever experienced and possibly see the betrayal in their eyes just seems like the most satisfying feeling in the world. Is that bad? I'm sure it's just a phase. I went through another one similar a few years ago, but now it's back and heightened a degree or two... or ten. I doubt I could ever do such a thing. I mean, to take another's life, I have no right. Still, sometimes, when I get in my right mind, I fear what I may do. And about that twitching thing, I've seen crazies do it in movies. Like, bend in awkward positions and eyes go all funny. It's not as drastic though.