Confused on the existence of children who are murderous

I was listening to a true crime podcast about a woman who committed unspeakable acts towards others starting at a young age. Her home life was overall loving, stable, and ideal with no trauma. And her sisters grew up to be wonderful ladies. The subject of the podcast was clearly born with some sort of mental disorder, as her tendencies were not developed from childhood circumstances/abuses. She was described as a narcissist from early childhood.

Before I explain further, I do understand we are born into a fallen world and that sin is inherent in us. Where I get confused is how a young child could have such evil tendencies (committing murder, SA of others, physical assault of animals) without having been exposed to something that would put it in their heads/make them aware of it at such a young age.

For example, many child SA victims go on to SA others, but the desire was not present prior and the behavior is usually a direct result of what they experienced. Without being SA’ed first, a prepubescent/very young child would likely not even know it was something that you could do to others. Like, if they aren’t exposed to it, where do these thoughts come from? How do they just know? How are young children incapable of empathy and capable of acts of murder? We are inherently sinful, but I just don’t understand if we are all born with the Holy Spirit + these children are born into loving homes, where does such intense evil come from?

It almost feels like they are born of Satan or possessed, but Satan is not a creator and I also don’t think you can be born possessed… It just irks me and I can’t wrap my mind around children just inherently knowing and being capable of evils beyond most adult comprehension. I also understand such cases are few and far between, but the podcast got me thinking about it.