Well that's the point, isn't it?
I dunno, I'm a bit too young for them myself so don't know a lot about them except they are a statement of female (and male) solidarity against crimes like this.
This is probably one man - he isn't going to attack women in numbers. He'll be a misfit, a coward and he'll most probably be getting off on creating such a climate of fear around himself. I'm not saying go out alone after dark on your own, but organise something to say women aren't just going to hide in their houses until he's caught - and in memory of those poor girls and their families.
There's been many a thread on here about the anger surrounding calls for women to stay in at night at times like this, this is just saying put it into action.