fjm for the link, there is an excellent and thought provoking post by hilzoy at Obsidian Wings, who helped a friend who was experiencing homicidal fantasies of the sort that occasionally end in tragedy.There were lots of books in the Counseling/Self-Help sections of bookstores with titles like: When Someone You Love Is Thinking Of Suicide; but there were no books called: When Someone You Love Is Thinking Of Going Postal. I went to the counseling center at the college I worked for, but they had very little help to offer... I tried to convince him to see a psychiatrist, and ultimately I succeeded, but "ultimately" here means after two and a half years, and then only by somewhat dubious means. It also means one and a half years after he bought the gun.
She says her friend's thoughts became stuck in a loop, or as she calls it a sphere, continually returning to the same thoughts.
The rut in which his thoughts turned round and round didn't really make any sense. One of the things that makes the image of the sphere work for me is that the person inside is genuinely trapped -- they're going around and around not because that's what actually makes sense, all things considered, but because while they ought to get out, somehow they just can't.
Another aspect of being trapped is that the thought processes become self-sustaining, separate from reality.
The cartoonish lack of detail in his thinking was an essential part of it. Would he turn himself in and go to jail? Try to escape? Kill himself? There was no answer. It was as though he thought that he was in a play, and when he had done this the curtain would ring down on what he thought of as his triumph, making all those annoying questions about what came next ridiculous.
I am not downplaying the extent to which chemical issues in the brain contribute to repetitive thoughts, and the failure to imagine reality strongly enough (and I think those two tendencies surely reinforce each other). But at the same time I think these are issues that we can also address through therapy and through self-help, and most importantly I think through friendship.
I would guess that everyone has had occasions when their thoughts started to dwell obsessively on a single matter (a lost love or a horrible incident perhaps) and occasions when a reality-check has been forgotten.