The photo alone tells the story.
Look at the difference in size of the two men. Look at the dead man’s stance, towering over the guy and crowding his personal space.
Clearly a bully with a temper.
And on the other guy’s porch.
I would have shot him.
An immediate threat, disparity of force
And from the photo shown, very difficult to retreat into the house.
He retreated into the house to get the gun then came back out.