Ten years before the hostage drama, a man stood on a bridge. This story isn’t about him so readers shouldn’t think about him now. Readers just need to know that the man stood there, staring at the water below and thinking about ending his life.
At this point, it’s unclear what this man has to do with the robber or the robbery/hostage drama. But the fact that he’s standing on a bridge is somewhat concerning, as he seems to be considering dying by suicide. Introducing the man and then leaping back to the hostage drama creates a sense of unease and uncertainty for the reader.