Its hard enough to be self aware as a adult towards danger, it's rare to see such behavior in pre-teens short of anxiety to do something.

There is only so much a parent can do instructing a child on a route to take home from a bus, plus possible courses of action for problems. From what I've heard, it was the first time the boy walked home alone. Horrible. Horrible.

I suppose the best chance is that you reinforce, constantly, never walk away with an adult unless they are uniformed police. Best to talk to an adult in a place of business, than on the street. Know parents phone numbers. Have an ID on them, my stay at home wife made 'business cards' on our computer with her name as "XXXX & XXXX's mom" to hand out to our kids friends parents. It has an up to date picture of DS & DD, plus our contact info.

Lastly, we need to allow our kids to grow and gain independence. However, not at the complete absence of observation if possible.