Aubrey could have stopped and asked why the heck a gun was pointed at him. Instead, Aubrey charged; he ran toward the man holding the gun and tried to take it away from him.
At that point the other man was in self defense mode.
The men attempted to stop Arbery twice before the video two trucks one in front on in back of Arbery.
Arbery did not run straight towards the gunman, instead he veered off the to right of the truck away from the gun man standing in the middle of the road. The gunman moves to the front of the truck to confront Arbery with shot gun at hand (this is aggravated assault, a felony in Georgia) Gunman fires first shot at Arbery.
Arbery was entitled to self defense, not the gunman, the gunman committed felony Aggravated Assault, you can’t commit a crime then claim self defense because your victim decided to defend himself. That is not how this works.