The way I viewed it, McGlockton gave Drejka a hard shove onto the parking lot, and advanced toward him while he was down. He intended to do some damage to Drejka. However, Drejka pulled the gun and then McGlockton backed off. You can make the case for something less than murder, but McGlockton got what he deserved.
He deserved to die for pushing a man to the pavement
Really
Have you ever been in a fight
If someone was disrespecting/barking at my wife, I might very well react just like McGlockton.
If I'm not mistaken, stand your ground requires that you cannot shoot if the threat is retreating. If that's correct, Drejka should be charged and the cop who failed to arrest Drejka should be educated or fired.
Drejka looks like a mental case and should mind his own business.