It appears that Mr. Dunn is toast, the fact that he did not call the cops after the incident raises a huge red flag
That has nothing to do with any form of legal trouble he may receive.
Dunn's problem, from a legal standpoint, is that he fired 2 volley's. The first volley was from inside his car, and the second is when he opened the door to get a better angle to continue firing upon a car speeding away. That second volley is what is going to land him in hot water period. Even if his first volley was legally justified, which I'm not saying it is at this point, the second volley would NEVER be considered legally justified anywhere.
In self defense you shoot to STOP a threat. That is not the same as saying you shoot to kill a threat. Killing a threat does stop it, but if you don't kill what you are shooting at and the threat has been stopped, then continuing to shoot is breaking the law. I've stated this a few times in this thread already.
The debate now isn't whether Dunn is going to serve prison time. THAT is a given based off the action I just outlined. I'm not sure of the punishment scale in Florida off the top of my head, but here in Texas that would be at a minimum a class A misdemeanor that would land him a year in prison for his actions of negligent discharge of a firearm.
What is up for debate was if the first shot was legally justified or not. Did the teens present a credible threat would make a reasonable person fear for their life or of receiving grave bodily harm? Right now we don't know for sure. Dunn's two claims were that Davis tried to exit his vehicle while making threats at him and that Dunn saq an object he construed as a weapon. Every party has corroborated that Davis was making threats at Dunn. Making verbal threats by themselves doesn't constitute a credible threat. Davis exiting the vehicle with a possible weapon does. Right now the statement from the teens is that Dunn fired based only off verbal threats from Davis. So without unbiased third party witness testimony, it's Dunn's word against the teen's word.
The ONLY piece of corroborating evidence Dunn may have in his favor is that if there was a weapon, that the teens may have drove off to dump the weapon. Which means the teens needed an outside party to pick up the weapon before it was found by police. The only way to verify that would be through phone records at the time. All the teens were seen by witness testimony to be on the phone when they drove off and came back. Who they were talking to we do not know right now. That is the only key piece of evidence in this case that would swing the case to prove Dunn's innocence.
Even lacking that piece evidence in Dunn's favor of proving there may have been a weapon, Dunn's case for self defense for firing the first volley is STILL strong. Despite his actions after the event. This is because of how the judicial system works. Dunn is INNOCENT until PROVEN guilty. Which means evidence must be brought by the state that PROVES guilt by a reasonable doubt. Testimony from the teens is not enough at this point to reach that burden of proof. Even if the testimony from the teens is the truth and Dunn is lying, the prosecution doesn't have the evidence to prove Dunn's testimony is a lie. Not with what we have right now. So even if it is murder, Dunn will most likely not get slapped with it. Mainly because the evidence shows that Davis was making threats to Dunn. This right now is corroborated by both parties and other witnesses that heard expletives being issued by Davis at Dunn.