Why didn't the responding officer try to engage verbally with Johnny Hurley? I think we can guess the guy wasn't pointing the weapon at the officer who shot him. [..]
Guessing is one thing. Evidence is another.
Here's another guess. A scenario from two different viewpoints:
Viewpoint 1:
Out of the blue, you witness a murder and good evidence that the killer intends to kill more people. You're not trained for this, let alone experienced in anything like this sort of situation. This is way out of your experience. You're highly stressed, but you keep it together and act. You kill the killer.
You're highly stressed. Primal situation, flight or fight instincts activated, adrenaline banging through you and now on top of that you've just shot someone. Five or six times. They're almost certainly dead. You're not in a calm, rational frame of mind. What next? Their gun. Get it away from them. Maybe unload it. Make it safe.
You hear a shout and instinctively turn towards it...
Viewpoint 2:
You're called to a shooting. Multiple shots fired, active shooter. You might be killed at any second. Keep that thought in your mind. Other people might be killed if you don't stop the killer. Mass shootings have happened before in your country and will probably happen again. This could easily be another one. It's your duty to prevent that. Keep that thought in your mind too. But mainly that you might be killed at any second. This second, maybe. Or the next. Or the next.
You find two bodies on the ground and a person holding a gun.
You "engage verbally" with them, ordering them to drop the weapon.
They turn to face you. With a gun in their hand. With two bodies on the ground nearby. You have a fraction of a second before they can shoot you...
Guns remove most or all of the time to think.