Just with regard to your title, I feel the need to point out that random/starnger-led violent crimes are at their lowest levels in history. Yes, some awful things still happen...but that's people for you. We live in one of the safest countries, during the safest/least violent period humans have ever known. We just know about EVERYTHING now, and compare it to our ideal view of what the world should be.
So yes, some awful crimes happen... but you're far more likely to be injured or killed on your every-day commute. All in all, we have an amazing quality of life with an extremely long life-expectancy. So many positives to focus on