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.
First of all, the "chase" term you use is one you're making up, not backed up by anything in the call transcripts. Zimmerman doesn't look to be in good enough physical shape to be outrunning a teenage athlete either. Martin looks like he's in good enough condition to run rings around Zimmerman, so thinking he was afraid of that guy "chasing" him seems fanciful.
As far a valid reason? Sure. When that suspicious stranger started running away, it made him look even more suspicious. Zimmerman most likely wanted the police to actually have a chance of finding Martin so they could talk to him. Zimmerman wanted to keep him in sight so he would know where to point the police to when they arrived.
Even though Zimmerman called Sanford Police (not 911?) to report a "suspicious person", it appears that this kid was, at least initially, doing nothing wrong.
So Zimmerman's pursuit, and Treyvon Martin's reaction to it, set into motion a tragic chain of events. If Trayvon attacked Zimmerman, the young man made a fatal error, although one which probably shouldn't have cost him his life. Given the circumstances, I think many of us can agree that Trayvon's intent was probably not murderous.
But, in the face of such as assault, it appears that Zimmerman did have a right to defend himself, since a physical assault of unknown lethality was initiated against him.
IMHO, even though it's tragic all around, I think the police decision not to charge Zimmerman (at least with anything approaching murder) is the correct one.
Zimmerman is apparently highly distraught over the incident as well.
This is a cautionary tale, which parenthetically has no bearing on Florida's "stand your ground" law.
Ummm cause he thought he was potentially criminal? Because there had been numerous burglaries and break-ins in the neighborhood. Because the crime rate of young black males is extremely high.