We are trying to recreate a dynamic and violent encounter using very few supposed facts. I say "supposed" facts, because everybody giving information in this story has an ax to grind.
I an not going to say that the justice system in Chicago is not without it's flaws, but the one verifiable fact that we have here is that the police looked into this matter and chose not to charge the shooter.
That tells us what happened about as much as Mueller's indictments tells us if those Russians committed any crimes relating to the election.