premising that if we want to talk about suicides we've to distinguish the various different cases and motivations for which they can happen
some/many happen at the end of a depression, which may take some time to fully develop, or which may take some time while depressed to come across a shocking happening to make the person snap and suicide, but there must be other cases, some suicide for personal life matters, others for sentimental matters, others for economy/work/future matters, we come across it sometimes in mangas too about the japs, and probably there are also other causes less publicized and less known
You know for sure when it's too late. Before then , its just about how good you are at understanding others. When people are involved no such scientific method exists. But for the teacher who does not take the problems of the child seriously, the kids who won't stop bullying, the parents who just have to many things going on to take a second look. Thoughts of killing ones self come when a person feels like they are powerless in a world that does not care.
In the end it is not for whom I would blame, every little role in a persons life is played by a person. It takes a combination of many of these small roles to push someone over the edge. Although there is always exceptions to the rule.
if i'm to follow that line of reasoning, surely there is some apathy on the road for a suicide, mostly in the suicider, and also in the people around him/her, but there are other sides of the matter
one is that a person who's (really) leaning to be suicidal is in a weak state, maybe literally or maybe just because they believe to be so, and i agree someone who's feeling weak should be helped if s/he's not surrounded by only jerks
but the help should not become just pampering them, but should be instead helping them to grow out of it, to have them standing on their own legs and being able to face the problems by themselfes, removing all the problems or blaming only the problems around them only leads to pamper them in not growing and remaining weak so the moment you stop pampering them they may return to be depressed/suicidal
an other side is how the perception of a person changes when they're depressed
it could be possible someone very depressed (or in any other altered state) may not even recognize the help when they're receiving it, making it more hard for them to being affected by help, and for who is helping to being able to reach them
you could still argue the helpers are not doing their best in helping the suicider, but it's important to remember even the helpers can be weak, and being actually unable to understand what is going on, or having a limited empathy, or other problems
also people usually instinctively try to avoid problems, so if they start to see a person in a weak state or a possible suicider or just a depressed person as a problem, they may just instinctively start to ignore them, they may then rationalize it as "too much hassle" "everyone is free for him/herself", but they're just acting instinctively
so what is possible to do?
if you happen to see and recognize one case try to do your best
but for any case happening everywhere else, they're just tragic happenings, both for the lack of will of the suicider to live on, both for the inability of the bystanders to do anything about it
(well, i'm considering the unwillingness to help being part of the inability to help)