Stand your ground law

I am also trying to wrap my mind around the concept that a person can stalk another person and when that person confronts them, kill them and claim self defense.  My understanding of the stand your ground law is that if you are physically threatened while just going about your business, then you have the right to shoot to kill instead of trying to get away.  Zimmerman left his car with a gun in hand to stalk someone just walking down the sidewalk.  He confronted him and the kid wound up dead.  Travyon Martin is every one's child.  This could have happened to any of our children.  Would I shoot someone if they were walking down the sidewalk in front of my house?  No!  Would I shoot someone if they were walking down the sidewalk and looking at my house? No!  Would I shoot someone for being in my yard? No!  Would I shoot someone who was breaking into my house?  Absolutely.   The difference here is that the person walking down the sidewalk is on public property, not personal property.  In my yard, yes, that is my property.  But if he is doing no harm why shoot?  Zimmerman shot Martin for walking down the sidewalk, a public sidewalk paid for by all the taxpayers.  It was not Zimmerman's personal property.  And he stalked the kid after being told not to.  So I fail to see how the stand your ground law can even remotely apply here unless you are saying that Trayvon Martin was defending himself.  My opinion, when Zimmerman left the car with that gun, someone was going to get shot.  This fool should never have been given a concealed permit.  He saw a gun as power.  Guns are not power.  They are dangerous and should be treated with utmost respect.  I was taught that if you carry a gun, you had better know how and when to use it.  Zimmerman did not know how or when to use this gun.