Suicide is never the action of a rational mind.
It is possible to reach a stage where life is so intolerable, that death looks like a preferable alternative, and this is the suicidal state.
To get there, an individual looses all sense of self, of support, of help, of a future, there is nothing left at all in the universe but THE PAIN.
One option is left. To hit back. To kill THE PAIN once and for all. And a final act of control is to do it violently. To spend your last seconds knowing that you got back your control when the end came - you hit THE PAIN back, and hit it hard.
From there comes the violent death - the train / jump / hanging / car crash - they are all 'hit back' approaches to death, and feel right and true and final.
It's not rational - but suicide is not rational. This is where you reach. This is the way out. With a feeling of control. Finally.