Am I going to become a serial killer or something?

I'm not going to tell you to reach out to God, as I don't know how you feel about religion. I know many people who aren't practicing any certain religion and are fine. However, if you want to go down the holy road, go ahead. It may help you.

I think you should first address your fantasies, try and find out exactly what gives you the pleasure. Harming animals isn't a good thing and there are plenty of better ways to take out your anger. You should try and find as many movies about how you feel, indulging your fantasies can sometimes help curb feelings like that. Though if they're giving you more ideas, I suggest you find a therapist that can help you, someone who specializes in that kind of stuff. Do some more research, start at Sociopath. Even if you don't think you are one, it's always better to understand yourself first. If you pick out things from other disorders you can put it together and find what you need and how to get help.