Is it normal to have violent fantasies?

I have been having some severe violent daydreams and usually its either me killing them or someone else doing it.
70 percent its about people I truely care about.15 percent is about people who are in just in my life. 5 percent it will involve some random person that I do not remember ever seeing. and the other 10 is people who i dislike And its almost always with a knife and slitting someones throat. It really bothers me, and it happens at the MOST random times. Like when I'm sitting in class and I'll imagine me just slitting one of the ppls throat.Or when I'm at home, or when im reading or on the computer,or whatever.
I was also abused when I was a kid/young teenager. I also had several trautimic events happen when i was an infant,which I was told about a few years ago.I'm worried becuz its been plaqueing me lately and I did not have these daydreams until the past week or so.I've never inteniolly hurt someone or an animal, though I have hit my dog,when she was being bad,but i saw what i was doing and managed to stop. Now I just put her out of my room or outside when I am angry with her.
I have always been a little on the violent side in my stories (which i almost never finsh),but its never been outside of that before. And yes, i watch horror movies,but I have not been watching them lately,so i am wondering why all of the sudden this is coming up. And why it is ppl (mostly) that I truely care about and would never do anything to hurt them. I have never been very violent. I DO have a temper,but again its never escalted into pyschical violence. So, is this normal and even if it is,what can i do to stop them? And i'm a lil scared here, and feel like I'm going crazy.