Of course, Zimmerman didn’t know this when he labeled him “suspicious” and decided to chase him.
So he was patrolling and noticed someone in a hoodie - and while probably every one of us owns a hooded sweatshirt, we know that most robberies occur by folks wearing hoodies to cover hair/ears, and most of their face. I can't help that - it is pretty common knowledge. Same goes for the slouchy pants - more likely to be worn by thugs, or those wanting to look like thugs, than the general population.
So Zimmerman is patrolling his neighborhood because he has taken the responsibility to watch for his neighbors at that time and he sees someone wearing a hoodie and doing something he feels is suspicious. Maybe it was a kid walking too close to apartments because he was new to the area and cutting closer to homes, maybe he was looking at cars he thought were nice - I"m not blaming the kid just saying something looked suspicious. I don't know about you but if I had someone getting too close to my car I would watch them - I do think Zimmerman should have called it in and allowed the police to handle it - but he didn't. And a witness says he was attacked - maybe the kid was defending himself, but the prior attack on a bus driver tells me that this story isn't as cut and dried as you think.