Nope, you don't - unless you're saying the cop was psychic.
What I'm saying is that the cop had been in combat. He knew what people look like who are coming at him to kill him and who had the means to do it. And to him, during the split-seconds he had to react, this perp didn't add up.
He said himself that he had his eyes glued onto the perp's hand in his pocket. He was well aware that they perp could pull a gun, and how much time he had to fire in self-defense. But remember, he had experience in exactly such situations, where he did indeed shoot to kill in war. So he felt he still had time.
But he also learned to trust his instincts in war. And his instincts told him this perp may well have wanted to be killed by a cop, but wasn't acting as if he was truly, actually a threat. And so, because this particular cop was actually trying with everything humanly possible to NOT take a life, he stretched his own timeline for reacting to the breaking point, because something that SHOULD add up, that he trusted to save his own life many times before - DIDN'T add up.
And, he was right.
One thing I do know is that you don't run backwards while someone is chasing you pretending to or actually having a weapon. Maybe he was sick that day in basic
I have a feeling that many here would have a different view if the last scene we saw from that body cam was looking up the barrel of .38 with the perp standing over the offecer and then the flash.