What will haunt you forever?

A few weeks ago, I was on the highway, going to Chicago. I was in the back with my sister, my mom was driving. I was on my phone when my sister told me to look out the window. It took me a while but then I saw him. A man. He was on top of a building, looking down. It looked like he was ready to jump, but what could we have done? We had passed the exit so we couldn't go back. We (my sister and I) decided not to tell anyone because they couldn't really do anything about it. I don't know if he actually jumped or if he was just hacking something out but the fact that he might have killed himself and I did nothing to stop him will always be at the back of my mind, eating at me.