You have a problem you are both victim and aggressor. Your aggression is most likely excusable, however you must be very careful not to say or do something that might get you convicted of a crime. In this respect you must act to defend yourself, and tell the police nothing.
HOWEVER, you are also the victim of a crime and as such you need to let the police know what happened, so that the crime can be investigated, and all subjects apprehended.
So... What do you do?
There is no easy answer. Some states have castle laws that may allow for the shooting of a home invader with very few questions asked, but let's take the same scenario and put it in the street outside your home. You are left with the same conundrum.
First, above all else, protect yourself. Only tell the police the very very very minimum of what happened. What is that?
I was afraid for my life.No more than this. They can see that you were involved and the other guy was involved. Only tell them that you were afraid for your life.
Next you must let the police know that the dead guy was the one who you were afraid for your life from. You tell them that. How?
I am willing to sign a complaint against that person.This tells the police that the dead guy is the one you were afraid of, without telling them any specifics of what went down. This is the only thing you say about the other guy. You are done talking about everything now. No more will you tell the police without a lawyer around.
The next two statements get you away from the police, and ensure that the police can not question you without an attorney present.
I require medical assistance from a doctor.This tells the police that you are not OK with just meeting paramedics. You want to see a doctor, and doctors are at the hospital, well away from the shooting. Think about it for a second... Do you think that you are in any shape to make rational decisions? You just killed a man in self defense. You are going to have all sorts of powerful emotions and hormones running through you. You need to calm down. And doctors have the things to do that. It will also get you away from the people who's job it is to put you in jail.
Finally, with your last statement you "lawyer up."
I wish to have my attorney present at any questioning.By law, the police are obligated to grant this request. The cannot deny your right to counsel.
You are done talking. If the police ask you any question other than if you want a Coke, you answer with the statements above. You do not say anything else. You must not waive your 5th and 4th amendment rights. They are there to protect you from the government, and if you open your mouth to say anything other than the above statements, you are voluntarily waiving those rights.
Any evidence that the police want to collect from you, even for "exclusionary" reasons, you only give up with a court order (warrant). Repeat like a mantra the statements.
I was afraid for my life.
I wish to sign a complaint against that person.
I require medical assistance from a doctor.
I wish to have my attorney present at any questioning.
You may end up spending a night or two in jail, but that is infinitely better than spending the rest of your life there, or having to explain a manslaughter or murder conviction at your next job interview.
Despite what the police will say, doing this does NOT make you look guilty. It does NOT make you look like you have something to hide. You are exercising your rights. They have a job to do, and they should do it. They don't come over to your office and help you with your job, why should you help them with their job? Especially if their job is to find something so that they can arrest you! Protect yourself, plan ahead. If you carry a gun, you MUST be willing to pull the trigger if need be. You train at the range to put rounds on target. It is silly not to prepare for what happens afterward.
If you have time, interview attorneys. This costs you nothing but time. Most lawyers will meet with you for free the first time to asses your needs as a client. You may never need them, but you may never need to use your gun either. Having an attorney you can call is very helpful if you get in to other trouble, or if you have legal issues, or questions. They are only a call away. Keep their card in your wallet with you CCW permit, because if you use one, you are going to need the other.