Roger, it's been my experience and i am of the opinion that the defective mentality of the masses (certain more moral individuals excepting)is that...
when a law is not enforced, [they feel] that a law is not in effect [meaning that it is just as *IF* no such law was passed] and therefore such a law can be ignored.
too many only fear the "sword", so to speak, (i.e., the potential personal consequences of their actions - if they even think of such) and have a purely selfish and self-centered outlook (or is it an "inlook" in this case of "self") - BTW, a focus purely on oneself, w/o consideration of other's needs/benefit is a well known characteristic of a young, immature child and sadly, many youths, and, IMHO, unfortunately, a growing number of adults. I've read that some psychologists consider only 25% of the adult population of the USA to meet the most basic definition of behaviorily "mature" - guess, this 25% figure speaks volumes about us adults.
i have law enforcement in my (non-immediate) family (a sister's husband). they are overworked, underappreciated, criticized by the general public and the Press no matter what decision they make in a difficult situation, and some, and this is no excuse, are just plain worn out from what they have to deal with each and every working day. others (fortunately very rare) find more glory and reputation/career enhancment in NOT preventing a crime, but in apprehending a criminal - sad, but on that very rare occasion true.
you are right about the incident you describe. there is enough blame to go around. even those NOT directly involved might ask themselves, "is there anything i could have done to prevent this?", or "could i have done more to possibly prevent this?", or "can i do anything to help prevent it from happening again?"
passing no judgement here on anyone , just expressing questions that i have posed to myself on various occasions over the years.