Urges to kill

So the past few months I've been having these urges about killing people and fantasies of how I would do it. I've been watching loads of serial killer films and documentarys to see how they kill and how they got rid of the body's, also how they got caught so I never make the mistakes they made. What's weird is that I'm a normal person when I'm out and when people see me, I don't kill animals or hurt people and I've never been abused, but I haven't had the best childhood, I witnessed my mam getting beaten by my dad when I was 5 and constantly getting cheated on by my sisters dad when I was about 10. Btw me and my sister have different dads. But when I'm walking across this quiet path on a mountain that's when I fantasise about killing someone and what I'd wear and what weapon I'd use. My plan would be to wear all black with gloves and a mask and I'd go to the path at about midnight so it would be dark and quiet and just wait for someone to walk pass me then I'd either stab them with a knife or hit them over the head with a hammer or a rock and then run somewhere so I can burn my clothes and hide the murder weapon so there's no evidence. I know this sounds insane which it is But If someone could help me or find me help I'd appreciate it a lot I've tried to tell my mam but I just can't get it out and don't have money for therapy or anything like that.