This is what I was told at my last CHL renewal, the instructor who was a 20+ year veteran of a Police Dept., and spent 9+ years as a homicide detective.
He said when you call 911, report what happened, briefly, request police and medical attention. The operator will begin 20 questions with you, then repeat exactly what you said the first time, request police and medical attention, then hang up. Everything you say to the 911 operator is being recorded, you have way too much adrenaline still pumping through your veins to engage in any extended conversations.
He also stated even though you may not think it now, after it happens, you will want to tell someone, it is very easy to get diahrea of the mouth. Once LEOs arrive, answer the basic questions, point out any witnesses, where the BG entered, what weapon he had. Now, answer questions to a point, once basic questions turn to 20 questions, like why do you carry a .45, why do you use Critical Defense ammo, etc, that is when you should shut up and tell them you want to comply, but need to speak with your attorney.
Also, remember, the first LEO to show up is normally just going to be a patrol officer, a supervisor NORMALLY will show up on scene and he/she NORMALLY will be the one to make the decision whether you will be detained or not.
Just my .02