I've witnessed two people stand on the edge of bridges over water. One was a criminal running away from police and drew quite a crowd, he was never going to jump - it was a matter of being backed into a corner. He was stood on the edge for perhaps half an hour before someone snatched him back and put the cuffs on.
The other was a truly desperate looking man who I happened up late one night stood on the edge of a bridge. We exchanged no words, just a look and the mutual understanding of pain and despair flashed between us. He had no fear, no apprehension or nerves, his face betrayed nothing but pain and perhaps for the first time in his struggle, a glimmer of hope just a footstep away.
Before I could catch another thought he had looked away again and taken his final step towards freedom. The police arrived swiftly behind me, someone else must have witnessed him and called them. I was ushered to the other side of the bridge whilst a cordon was erected, it was dark so I couldn't see what was happening in the river below, but the newspaper mentioned a suicide the next day so he was evidently successful.
In my mind, there are some people who absolutely cannot be talked back from the edge, their decision is planned, rational, final and not impulsive - I saw that in the second man's eyes and that is a look that will stay with me for the rest of my life.