I have always found that looking at how law enforcement officers react to officer-involved shootings can serve as an effective guide. In the majority of police departments, officers involved in a shooting only have to answer a few "Public Safety" questions prior to meeting with their attorney and writing a formal statement. These questions are different versions of; (1) "How many shots did you fire and in what direction?"; (2) "Are there any additional suspects on the loose?"; and (3) "Do you know of anyone else who might be injured?" These questions generally must be answered by officers at the scene so that investigators can locate anyone who poses a danger to the public, or any parties that may be injured.
Civilians are not under any obligation to answer any questions at all without an attorney present. If someone involved in a shooting chooses to speak with police, I would not recommend providing any information beyond the answers to these three questions and your basic identification prior to meeting with an attorney. It is quite possible for a shooter to state that they feared for their life or the life of another innocent party at the time they acted, and that they would like to speak with their attorney before answering any more questions, without appearing rude or combative. Civilians need to be mindful that they are most likely being filmed, and I would recommend being as polite and respectful as possible when asserting your rights. You are within your rights to say, "F you, I don't have to tell you anything!", but it might not play well to a jury or a DA deciding if he or she should file charges in relation to a shooting.