Without revisiting our differences of opinion on allowing nutjobs to wander freely in society, it is apparent that this man had problems for quite some time. Whether due to an untreated mental illness or caused/aggravated by substance abuse, it placed him in a weaked state and that's the entire basis of natural selection. The strong survive only because the weak cannot.
I'm sure that an autopsy will reveal if any foul play was involved and what his toxological state was at the time of his death. Whatever the course of events that led to his death, we all need to accept that "survival of the fittest" is a universal, natural law that we may not like, but cannot change.
As for your proposal regarding fences, I will submit that any property owner with a retention pond who does not fence it off is begging for a lawsuit. The primary concern is children who are old enough to be out without parental supervision, but still young enough to be idiots. One can argue that an unfenced retention pond, just like an unfenced pool or cellular tower poses an "attractive nuisance" to the young mind.
I'm not in favor of requiring fences, but you can bet a large sum of money that if I had a pond on my property, it would be fenced.
More information about formatting options