I tend to think Drejka is in a bit of trouble. I believe that HE was scared for his life when he pulled the trigger. The case is, as I said, going to come down to whether he can convince a Jury that that fear was reasonable given the circumstances he was in. And he may very well have a hard time doing that.
It's worth remembering as De Selby talks himself in circles about another Florida SD shooting, that Drejka didn't start a fight with McGlockton. Drejka started an altercation (there was no physical component, and as far as we know now not even threats of a physical nature) with McGlockton's female companion. McGlockton started the fight, and he did it with no warning, by escalating a situation he wasn't involved in to a physical assault.
Yes, Drejka made some poor choices, and he did so while carrying a weapon. He may very well go to jail for manslaughter. He may very well be guilty of manslaughter. (those two do not necessarily go together) However, McGlockton is the one that "started a fight over a parking spot", and that's not nothing. Drejka isn't actually the aggressor here.
ETA: Hawk and I cross posted, but yup.