This reminds me of the pricker method for killing someone that spies use. Super hard to defend against in a crowd.

I still say that I'm pleasantly surprised there aren't more things like this happening all the time. In the US specifically even though we have fallen a lot morally if there really were many people that wanted to kill masses of people it would not be that hard to do. I don't think we really realize how fortunate we are and we take so much for granted.