Scott’s weapon was a Kimber 1911-type gun. It had its hammer down after the shooting, which means Scott was carrying with no round in the chamber. To fire it, he would have had to pull the gun, rack the slide, and then fire.
It may be that since he was aware it was impossible to shoot his gun without several steps, he didn’t think about how a cop - not knowing what type weapon it was - would interpret an attempt to disarm. Or maybe he thought that was the simplest was to calm things down.
Could the cop legally fire as soon as he touched the weapon? Maybe. If the cop believed his life was in danger, then yes - even ‘tho Scott obviously (in retrospect) had no intent to shoot. However, a cop so spring loaded to shoot that he didn’t notice the movements were slow, or that the gun was still in its holster (the cop who started the shooting testified he didn’t know the gun was in a holster until after the shooting was over), is a cop who needs to find a new line of work.
The cop has shot 3 times in 4 years, killing 2. There is no way he has the right temperament or judgment for being a cop.
As for the other two - if you continue to fire after the guy is face down on the ground, you aren’t ready to be a cop either. Find other work until you gain some self-control and judgment.
I suggest making license plates.
While it's not particularly recommended for a 1911 type weapon, some folks will lower the hammer on a loaded chamber. This was actually fairly common in some law enforcement circles who didn't want the general public seeing them walking around with a "cocked" weapon. Depending on the circumstances, I do the same thing with my CZ75B which is a double action that doesn't have a decocking lever. I'm not sure if the Para-Ord 1911 types with the "Light Double Action" have a decocking lever, but they could also be carried with a hammer down on a live chamber and ready to go with just a squeeze of the trigger.
...certainly it's a trivial point, and regardless, what the LVPD did to Erik Scott appears to be completely unwarranted, and they should be charged with negligent homicide at the bare minimum.