Haven't watched the video for a while. Trying to remember; did the guy come out of the store and go directly to push the shooter down, or did they exchange words for a minute?
The guy came out of the store, went directly to the shooter and shoved him to the ground. They didn't exchange words that I could see. I actually thought the guy stepped toward to the shooter after shoving him to the ground. It looked like he backed up once he saw the shooter pull out his gun.
After that, there was no need to shoot someone.