Brother with 25 years experience on the street then up through the ranks to command says, "Never, ever talk to the police. They aren't you're friends and they aren't there to help you."
That's great advice if you are a criminal. There is literally nothing a criminal can say that will help his case... because he's guilty.
In a valid self-defense case though, you are innocent. You are the victim, and that's what this whole 'say nothing at all' mindset misses. That video above is aimed at CRIMINALS. People who really committed the crime they are being questioned about. Most police are used to dealing with criminals who say nothing, and if you do that they will almost automatically put you in that same category.
On the other hand, if you describe the basics of what happened ("I was attacked by that man, he had that gun, those people there saw the attack") and politely tell the police that you will gladly give a full statement once you have had a chance to speak with your lawyer, they won't be pegging you as a criminal.... After all, criminals don't point out evidence and witnesses, or offer to make a full statement.
I'm also not really sure about hanging up on 911.
If you are in public I would think you would want to stay on the line no matter what, just to make sure that the dispatcher can act as a relay between you and the approaching officers. You need to make sure they have a good description of you, and are aware that you are the victim here, not the attacker. Simply being on the phone with 911 helps establish this.
You don't have to answer any questions the dispatcher asks, just keep it to where you are, what you look like like and that you were attacked. As mentioned above, those calls are recorded, so you do want to keep it to the bare minimum.
If you disconnect the call, the cops will be rolling up and see a guy standing over a guy bleeding out on the ground, and probably treat you like the attacker. You won't be able to hand them the phone and ask them to verify with dispatch that you called them. That the man lying in a pool of blood is the actual attacker.