I'll ignore your little jab and take you seriously.
Keep in mind that each state can have slightly different laws about this.
In many states, you can use deadly force to respond to a threat of GBH, great bodily harm. You don't have to fear for your life, just GBH.
If you are being beaten up with fists, you can shoot/stab your attacker. You need not respond "in kind". You need only have a reasonable fear of GBH.
You are not required to wait until your attacker makes progress on you, either. You need only reasonably fear that GBH was about to happen to you.
To analyze any particular incident, you would need to look at the laws of the state where it occurred.
What you get away with clean in Florida, you might go to jail for in New York, for example.
Police officers generally get a wide latitude when they shoot someone. In this case, with what I have already heard, I think it's very unlikely that a jury would vote to convict the officer anyway.