If you look at about the :20 mark, just after the guy was shoved to the ground, the perp began walking towards him, and only retreated when the weapon was drawn.
However, he did back off after that.
So yeah, technically justifiable, but I don’t think the incident rises to the level of ending someone’s life.
It does rise to the level of ending someone’s life, because exactly what happened.
That’s how fast you can lose your life in this world.