What is the most disturbing thing someone has ever admitted to you?

A wacky guy from the old neighborhood admitted he was involved with a couple other guys in pulling a lever that routed a train from the main track to a maintenance spur. Then, they couldn't get it changed back. The train was coming, they panicked and ran like hell. The train derailed. It was quite the mess. Fortunately no one was killed. Everyone in the neighborhood had an idea who it was, but no one could ever prove it. He let it slip over a few cocktails decades later. I'm not sure if he was making it up or was actually involved, but my guess would be he was involved in some way. Karma caught up with him and he's deceased now.