So many senseless things like this seem to be happening all over. If you are the kind of person that cannot imagine doing such a thing, it is so hard to wrap your head around how someone could choose and carry out these actions deliberately.
I try to be aware and as I age, even more so. I know that doesn't mean I will absolutely avoid being a victim of something, but I do try to make choices of where I go and what I participate in, based on what I think the gamble will be for me as I am now.
It is a shame though, that it has to be this way.
Harming people like this takes a special breed of human and yep, there's plenty of them out there all willing to harm others because of their religious beliefs and other reasons also.
You're on the right track, being aware, and minimising your risk seems to me like a much better state to be in than to be careless and oblivious. People are so reliant on others these days that they forget they have the means to mitigate risk for themselves.