he knew what he was doing was wrong
He darn well knew or else he would not have been sneaking around and doing it to them while they slept. Yes other times he did it while they awake but at first it was while they were sleeping. He did not want to get caught and they scream.
“he knew what he was doing was wrong”
Of course he did just like murder or stealing etc.
However the ability to grasp the amount of harm you are doing to another is not all the way there yet.
I don’t support the death penalty for children, nor is it biblical. Death penalty is for ADULTS, and we can debate what an adult is, but it certainly is not a 12 year old.