Nearly every shooting that ends in a death turns into a self-defense narrative almost immediately.
The desperate need for “Good guy with a gun” stories is very very high as it justifies a narrative that many people have invested a lot of emotional energy into.
That can’t be helped. They will stick with that narrative regardless of facts. That’s not to say good-guy-with-a-gun doesn’t happen at all. It does. Sometimes.
This isn’t one of those times.