Law is not my forte, so I can't pull an arbitrary number out of my ass to determine at what age a child can be held legally responsible for a crime. All I know is that if some kid charged at me with a knife, the last thing on my mind would be me wondering whether that kid is either close to being 11 or 17 years old.
Why do you keep changing the situation and topic?
You posted 3-5 year olds and then said anyone can be a terrorist. Then changed it to 11-17 year old's running at you with a knife. You are the gift that keeps on giving.