It’s one thing to “step in to protect her” in the situation of a verbal argument. A “man” with an obvious considerable physical advantage would physically interpose himself, not blindside the other guy & violently knock him to the pavement.
The Killer was up in her face.
It is clear that he did not have to shoot since he pointed the gun for several seconds and the BG backed off.
It looked like he felt the shove was enough to handle the situation. The new poster-child for no CC and Second amendment thought otherwise.