Because somewhere along the line, someone decided this wasn't even worthy of assault. It's not like you would go in and charge yourself.
It's a criminal justice system bungling of the highest order and it's what caused all of that. That it's been a month and he hasn't been charged, is a total joke. There's not much of an investigation here, the guy discharged a weapon and killed someone. You throw the book at him and the grand jury can decide what is what.
This is the same area of Florida that fucked up the Casey Anthony case beyond all recognition. Honestly they'd probably find a way to lose the case when/if it happens.