A good scenario, tailored to a cut and dry outcome. Perhaps a future variant could include a downed suspect who is still conscious and in possession of a firearm. Also, my wife pointed out that the shooter may have been in a better tactical position if he had stayed in the corner, so that: 1) His back was covered; and 2) There would be no accusation from witnesses that he was "looking for trouble" when he checked around the car and area. I know, I know, he was looking for threats, but her point does have some validity. I also noted that he didn't keep his attention on the downed suspect, in case she recovered and continued the assault, ditched the weapon, signaled a partner, etc. If I were in his shoes, and moved out to check the area, I would move away from her. If she is not unconscious or dead, she certainly had the opportunity to reach out and grab or stab him.
While I agree that he should not interact with her after the shooting, I must interject some variables. If she had the potential to continue the attack, I feel it would be dangerous but appropriate in some situations to kick away the weapon. Also, while I have no legal duty to act in this scenario, I am a certified Paramedic, and I'm sure a crafty attorney could make me look bad for not treating the suspect.