This seems intuitively unlikely to me. For example, The Maui News reports:
A 44-year-old Napili woman died Sunday afternoon as police said Monday she had shot herself at the Ukumehame Firing Range while taking a firearms education safety class.I dunno what percentage of suicides are spur-of-the-moment. I had a friend and colleague once who was under a lot of stress (alcoholic, out of work, broke) who was killed when his truck ran into a bridge abutment at highway speed. Most of his friends thought it was suicide, though whether planned or spur-of-the-moment we could not guess. I couldn't anyway.
Around 3:40 p.m. after loading a .22 caliber revolver, the female "without any indications" placed the barrel of the gun under her chin and pulled the trigger, police said.
The instructors who witnessed the incident had no time to react before the weapon was fired, police said.
But I am reminded of a study done of people who had jumped off the Golden Gate Bridge and survived (sample size, about a dozen). Every single one said that on the way down, he thought, this isn't the solution.
This seems borne out by the fact that nobody jumps off the Golden Gate Bridge twice; although, bizarrely, an Iraqi man who jumped and survived did go back a second time, when he lowered himself of the edge in a garbage can and threatened to cut the rope.
Near as anyone can figure, he didn't but the rope slipped. He did not get a third chance.
Unless you live in a very bad neighborhood indeed, the chance that somebody (maybe you) in your household will have "suicidal ideations" is far higher than the chance that some home invader will break in and try to threaten you.