Actually you're not innocent until proven guilty, it says nothing about the justice system being involved.
So if you're trying rape, steal, or murder someone, it's pretty obvious you're guilty. Unless you deny what you see plainly infront of your eyes?
It's sad you feel as if though people aren't allowed to protect themself without having to go through a bureaucracy, shooting someone who is commiting evil acts against yourself and harming you or loved ones isn't cruel or unusual punishment, if anything, it's more merciful, or do you think having the burden of knowing your time is coming, instead of dying on the spot, is less cruel?
Being a democracy has absolutely nothing to do with being attacked, and defending yourself.
You seriously need some mental help. Therapists exist, go check one out.