To say he "strapped on a gun" before going outside sounds like media skewing. Whenever I go outside, I "strap on".
On the other hand he could have left before brandishing. After he did draw, and threats were made, that's where it gets a bit hairy. As I stated earlier, from the video, it seems like he was never in the neighbors yard but in the street. SYG applies to places where an individual has a legal right to be.
After he drew and one guy says that he will go get his and be equal is where he might actually started to really feel scared. Obviously he was attacked, hence the shaking of the camera and then the shot. His fear was realized, but the questions for me are;
Did he have a legal right to document the obnoxious party? Yes.
Was he armed legally? Yes.
Did he brandish the firearm? Yes, but after a crowd of drunks were advancing on him.
Could he have left safely before brandishing? Yes, but did he legally have to being in the street where it appears he was when the actual confrontation started?
Not saying he is in the right or wrong I can definitely see arguments for both.
"The bended knee is not a tradition of our Corps"-LtGen. Holland M "Howlin' Mad" Smith, USMC,1949
Have you forgotten yet? Look down and swear by the slain of the War that you'll NEVER forget. [Siegfried Sassoon,"Aftermath,"1919]