And after all the various countermeasures considered... Here's the first one I'd advocate - one of the topics I had to learn in one of the many classes I was sent to when I took over my agency's Community Patrol outfit (great fun - it included everything from training on down - I even had our marine patrol unit - all at the same time...) was something called CPTED (short for crime prevention through environmental design...). The basic idea was that you could prevent some kinds of crime (or greatly diminish them) by how you either designed the environment in the first place - or how you planned public events.... Hmmm, in this case the first item on my agenda would be... wait for it.... No public concerts right next to (or within shooting range of) nice tall buildings.... Just think - the organizers had their choice of venues and they chose the one that turned out badly. I'm not criticizing them for not thinking of the un-thinkable - I wouldn't have either.... I'll bet, though, in future -outdoor concerts will be held away from places that are natural high elevation ambush points.... if at all possible.
The most common feature of places designed using CPTED principles are things like walls - that you can see through (solid perimeter walls create places where bad things can occur un-observed - pay attention to how the proposed new border fences are built...). Apartment buildings where the parking lots aren't under the building - but out where the tenants can look out of their windows and actually see their own cars... These are simple steps that cost little if anything extra - but actually do cut down on crime opportunities without being obvious about it... By the way, I have no idea whether this kind of training is still called CPTED - so for young officers (and citizens wanting to learn a bit about this sort of stuff) you might have to look a bit through course listings at your local academy - or college that offers police science course work...
