I agree -- until you get to here:
What does that say about the support, social and professional, that he believed was available to him?

It doesn't say anything. Whether the support was extraordinarily good, or extraordinarily bad, this is not an average citizen. This is a man trained to kill people. That's a very large thing. Has he ever actually taken a life, or even shot at anyone? Chances say no. the average LEO will draw his piece in defense maybe once in a career. The expectancy of the department, however, is one of "manly perfection." Testosterone runs high in that ready-room, and this is true of any organization with people trained in the eventual killing fellow human beings. A hell of a lot is expected of these folks, one of which is being able to deal with these same fellow human beings' personal issues -- as well as his/her own.

Why would he place the deaths of 4 total strangers ahead of the lives of his 6 children?

Self analyses are a constant. Everything about his own persona is self-studied on a daily basis. A dyslexic slip, something that may have benignly occurred time and again in his past, is a suddenly critical error that results in death, and he finds himself lacking -- as well as far too ashamed to seek help for a problem he had been hiding/avoiding all these years. Yes, that’s all it probably was, and to the point of killing himself. Just a little typo, and those he was sworn to protect are now dead.

The department will never agree with any of that, though I think in-house changes are probably going on today -- changes that will likely do little to prevent similar tragedies in the future, simply because the job is so unbelievably demanding.

What is required to fight this is mandatory monthly counseling sessions for all field officers, and mandatory, intense sessions following association with life-threatening/life-taking situations.

This, of course, requires both department time, and department funding, neither of which are ever easy to locate.

Just my thoughts on it,
Dan