He had a valid reason. He felt Tray was suspicious and he made a call to the police to report him. The dispatcher never told him not to follow him, he said that's not necessary. There's a difference.
Really? I disagree. First of all Z isn't that much bigger. Second, Tray is a young fit/trim kid vs Z who is less than athletic looking older guy...I'd take that odds and believe Tray did too. Along your lines though, I say the same thing when I see the news and they report kids taking shots at cops. They don't care, they don't think through the consequences and they typically believe they are invincible. I don't think tray just exchanged words and I personally don't see Z starting a fist fight. I could see him pulling a gun right away, but evidence doesn't support that happening. My guess is Z started a verbal questioning and acted tough, tray turned and got in his face and ended up taking him to the ground, where Z then cryed for help, then out of desperation grabbed his gun and Tray got what he didn't expect and found out he wasn't invincible.