My first post was a way of making fun of Bogative's response, because although we don't know a great many things, I think we know enough to draw some very easy conclusions, and although I am not a lawyer, I think I understand the basic legal questions here.
What we see on the video is that the men in/near the pickup truck were behaving in a threatening manner toward the jogger (by deliberately blocking his way.) It also appears that part of their threatening manner was display of and possibly pointing a weapon at the jogger. I say "appears" because I didn't watch the video frame by frame to be absolutely certain that the driver was threatening the jogger with the gun, but it sure seemed that way.
At that point, a reasonable person in the jogger's position would believe that he was in imminent danger of death or great bodily harm, and that escape from that situation was impossible. (i.e. you can't run away from a bullet, and the fact that they deliberately blocked his path would be perceived by a reasonable person as an aggressive act. A reasonable person would fear being shot in the back.)
In doing this, the men in the pickup truck have committed a crime. You can't go around pointing guns at people. You just can't. In some states, there's an exception if you happen to be in your house and he's breaking in, and in all states there's an exception if you are under a reasonable fear of death or great bodily harm, but there is no way any of those circumstances applied to the pickup truck people in this video. It's illegal to go pointing guns at people. Someone could get hurt.
So, the jogger's action, attempting to wrest the gun away from the driver, is justified. Preceiving himself to be under a threat of death or great bodily harm, he is justified in taking action to neutralize that threat, which he did, unsuccessfully.
Now, as a matter of principle, I must say that everyone is entitled to a fair trial, and even to the presumption of innocence, so we must remain open to the theoretical possibility that some future evidence will be presented that makes it clear that there was some extremely important but currently unknown (to us) piece of evidence that would put a completely different spin on what appears to have happened.
However, based on preliminary evidence, it seems these guys are guilty as sin. I suspect both of them, not just the man with the shotgun, because I think both of them brandished weapons. I would have to watch the video again to be sure about the guy in the bed of the truck, but I think he did.
Prosecutors and/or juries will have to decide exactly what charges will be filed and what the convictions will be, but if it isn't something, I will be very surprised, and the people of Georgia will be very angry.