I'm going to yell at this kid for staring at me
why do you want to yell at this kid?
It's an impolite behavior of children to stare at people.
The kid is rude to stare at you but yelling won't help the situation. It would be better to just turn away.
What if this kid becomes a serial killer later in their life?
Your fear is irrational and absurd. Kids are naturally curious about everything and they stare at people, it's not creepy. You should be friendly with that kid and talk to them nicely instead of yelling.