1) You do not know that as a fact. It is just as probably that someone walking slowly in the rain looking at cars and windows was scoping out a target!
2) If he were simply walking home, why the heck did he turn around and go back after Zimmerman, rather than going home. Fact is, he ran away from Zimmerman and clearly could have just gone home, but chose to confront!
3) When do we start blaming the parents? They had a problem child on their hands and were letting him freely roam around at night?