The facts and circumstances of the incident, as they appear to the first responding officers who ask you and other witnesses (if any) what happened, will probably determine whether you are charged with murder or left at the scene to go on living your life a free man while the cops, detectives, and later the DA consider filing charges.
Now you have to realize that "somebody" has to make out a self-defense claim, to avoid somebody being charged with murder for that dead body at your feet.
If YOU don't tell the cops it was self-defense and that it was necessary to shoot him to save yourself (your family, whatever), then who will? Is there another witness to do it?
If you lawyer up right away, and say nothing to explain your conduct at all, I think you would be charged with murder.
Then a few days later when your lawyer meets you in jail, you can consult with your lawyer and then tell your self-defense story to the detectives, which should prompt the DA's office to agree to a big reduction of your bond now, and probably dropping the charges entirely soon after.
(If your story fits all the physical evidence at the scene. If it is believable. If it is not contradicted by what other witnesses have said.)