I wonder about this, too.
One of the articles linked in this thread said he was the "self-appointed" neighborhood watch captain. So I wonder if he even got any training.
I can understand, if there's a spate of crime in your neighborhood, the desire to catch who's responsible and the feeling of frustration that the perp hasn't been caught. I can also understand seeing someone you don't know walking around in your neighborhood in the dark and wondering if maybe they're up to something - if you saw an old lady walking around vs. a lone teenager, who would you be more suspicious of? So I could understand, in those circumstances, calling the police to check it out.
What I don't understand is following him, getting out of the car and chasing him while packing heat. Also, I'm curious how someone like GZ managed to catch up to someone like Tray, who was 10 years younger, a lot thinner and probably faster. He must have been really determined to catch him. If only he had just waited for the police. It doesn't sound like Tray was doing anything wrong. I know I'd be trying to run if someone was following me in a car and/or on foot.
What did GZ expect to accomplish, anyway? Could the police have detained Tray and run his fingerprints to see if he was the burglar - just on GZ's say so? What did GZ want to happen?