in a lifetime, 15% of Americans have witnessed a shooting, 25% have been threatened with a gun, 12% have been shot at, and 4% have been shot.
You're not actually suggesting 'once in a lifetime' falls under "normal occurrence", are you?
This is also a partial goalpost move, since the original sentiment responded to was asserting that "being shot at" was normal, and you're now citing other things like 'seeing someone else shoot someone', obviously an event that's much more common relatively speaking (but still nowhere near "normal" for the average American).