Tip for everything
I figured this out a while ago, but was too lazy to post it.
Only enemies that you see on your screen will attack you, or an enemy you looked at who has started an attack. When a group of demons pop up and you need help, turn around and look at the corner, no one will attack you until you are able to see them on your camera. This is useful for clearing out tons of enemies.
P.S. I think this just may be a Capcom thing, works in RE6 in most cases as well.