He was on the way to the store when he saw a person behaving suspiciously. Anyone - neighborhood watch or not - would call it in. GZ called 911. If you watch his reenactment for the Sanford PD he explains why he went down the walkway... he reasoned it would be the street sign the PD would need.
Should he have driven down the sidewalk between the buildings?
Nothing NOTHING justifies TM’s attack.
Nothing justifies Martin’s attack. GZ did nothing illegal. However, GZ could be home drinking beer instead of sitting in the courtroom. If you ever volunteer for neighborhood watch and you see something suspicious, I would suggest that you stay in the car. Your decisions and mileage may vary.