How to control such thoughts?

Fed, it's very important to distinguish between fantasy and reality. What happens in your head, much like a video game, should never cross into reality. If you feel you have urges to act your fantasies, it's very important to seek medical care as soon as possible. You should speak to a counselor, a psychologist, or an older, wiser family member. It's crucial that you don't let fantasies get out of hand. Many people have all kinds of thoughts in their heads, where a thought becomes an action is what distinguishes one from a law abiding citizen to a murderer or rapist. Make sure you seek care if you feel the thoughts are getting the better of you.