I was shocked to find that when I heard of this that I wasn't completely surprised: that this type of senseless or pointless or gratuitous (or any other adjective) killing seemingly for the sake of it, and with no apparent aim other than to shock, seems almost normal now is utterly obscene. Then this evening there is an incident in Finland and people have been killed, although the details of this aren't yet clear as regards terrorism.
It raises all sorts of anxieties: where is safe and who can be trusted, where the danger is that everywhere and everyone who can be thought of, rightly or wrongly, as representing the 'other' is viewed with suspicion - but without knowing who the enemy is then not only can they not be tackled the risk is that anxiety causes some to see everyone who looks like the 'other' in their eyes as a risk, especially where those doing this stuff turn out to be otherwise unremarkable and aren't known to security services.
I've no idea where we go from here - we were planning to take our grandchildren to France again next year but already today my elder daughter (their mother) is wondering if it is safe for them to leave the UK - I said to her there is no guarantee we'd be any safer holidaying in, say, Cornwall than we would in Royan - and just 5 years ago we'd have no such worries, and that is depressing.