That's where the psychopath part comes in. It could start with stepping on insects or playing call of duty. All of a sudden they start wondering what it would be like to actually take a "real" life, and eventually they start plotting.I’m not sure why someone wants to experience that.
There's a crazy amount of documented stories of surgeons that decided they gone start testing their own hypotheses on regular people, and only got caught after multiple bodies. Also, when people are at or near the top, some start to wonder how much they can get away with without any suspicion.
The world is completely fukked up

