I believe I would give a short account of my actions, emphasizing my fear and stressing that I just wanted them to stop what they were doing, after I had calmed down a bit.
Any detailed account would be later after I had time to collect my thoughts.
You're half right. Emphasize that you are too upset to give a statement (which you want to be if you've shot someone) and that after you've had time to compose yourself (and call your lawyer) you will be glad to meet with them. You don't have to express the desire to have a lawyer, unless you are taken into custody (hence the "am I free to go" question).