Boy hiding from “hollow people”

I can only remember vague parts but it was a YA book I read around 2006ish.

There was a boy whos parents were killed by “hollow people” or “echos” that looked like humans but had nothing inside them & were just avatars for some kind of malicious force that was coming after the boy.

He ends up in a ‘mind prison’ at one point and has to fight through his trauma to escape