Once they’re running from you they are no longer a threat. And the push down could’ve caused head trauma, and the suspect was already retreating so it wasn’t necessary.

I’m not a nut, I just don’t defend rampant thuggery in the guise of “home defense”. Seen too many “they were running away when shot in the back” stories where the shooter gets away with it because of right wing style home defense laws, aka you can kill anyone for any reason even at the moment they’re not actually a threat to you. That’s called murder. Or assault.