Then why don't you know that he didn't call 911 that night but rather called the police department number? As was the case with most of the 40 or so calls he made over multiple years. On one of the calls (about an open garage door) he says that the police told them in the neighborhood watch program training to call in if they saw anything suspicious.
With him being a neighborhood watch volunteer for a few years, I'm sure he was in the habit of seeing what people he saw around in that gated community, so he would know who might be out of place. In light of some recent crimes in the neighborhood, I guess this night he considered a six foot tall, young black male that he had never seen before walking through the neighborhood suspicious enough to warrant calling it in.
Okay, so let’s say he had a reason to call 911 as he was being safe. I would say that based on the fact that he was innocent, Martin had a reason to be on edge having accusations thrown his way. Can you name one good and solid reason for Zimmerman to chase after him? That, more then any other fact in this case, is what turned this into a tragedy. It likely caused Martin to feel like he was in danger, if he sits in his car or goes inside, none of this happens. Zimmerman witnessed no crime being committed, I could feel empathetic if he watched the kid hop out of someone’s window.