Some years ago there were two suicides in my area, both horrific and very public. From the little info that I have, it seems that both were unplanned spontaneous events. This was for me truly frightening. It felt like a 'gremlin' exists and can come up any time. I have never truly overcome this fear.
I would be very interested to know of the experience or knowledge of others in this area.
I have more experience in this area than most would care to.
A lack of impulse control is perhaps the unifying feature of most suicides and homicides. In patients who have bipolar disorder (with phases of depression and phases of mania) the vast majority commit suicide while in mania not in depression.
It is one of the reasons for restricting access to firearms, especially in people with psychiatric problems. The decision to kill oneself is often made spontaneously, in a background of mental instability. Then the time that it takes to drive to a large bridge or climb a cliff and jump off, as well as the time it takes to succumb to drugs, or set up a noose is enough to calm them down. But there is not enough time between picking up a gun and firing it at yourself, to take a time out and reconsider before pulling the trigger.
No gremlins or demonic possessions. Just impulse control issues in a background of depression.
However, to commit suicide in public view is rather unusual, except in certain cultural situations, and where the person is trying to make a statement, usually “against” someone who upsets them. A “This will show them!” sort of statement. These tend to be the more dramatic suicides.