Massad Ayoob is one of the leading experts in the US on defensive shooting.  He has written countless articles and books on the subject and has trained both civilians and law enforcement on the subject.  Here are his five key things you should do if you are involved in a defensive shooting.

1. Establish the reason you shot the perpetrator (active dynamics of the shooting).
2. Inform the police that you will file a complaint against the perpetrator (this serves to reinforce the active dynamics stated in #1.).
3. Point out evidence to the police, but don’t touch the evidence.
4. Point out any witnesses and those that might have seen the incident (if they have left the scene then provide descriptions to the police so they can seek them).
5. Inform the police you have been through a very traumatic event and that you intend to fully cooperate with the investigation once you have spoken with your attorney.  At this point, stop talking until you are represented by an attorney!