Years back, I was working at a grocery store. Our regular milk delivery driver was on paternity leave, and I had time to chat with the guy filling in - nice guy, he told me normally does desk work but was filling in while our regular was out. A couple hours later, the next store on their route called and asked me if we had received our milk delivery. I told him we had, didn't think much of it until I learned about a multi-car accident on the freeway. If I recall correctly, it was foggy, a car cut in front of the semi carrying milk and he hit his breaks, semi tipped and a few folks died in a pile-up.

I never saw that guy again, I'm fairly certain he survived but can't imagine the guilt someone would have after that.