I was once fired back when I was 19.
I was working at a Jiffy Lube and after improperly tuning a customer's car (she had already left), I was given a stern reprimand.
Turns out, the poor lady got in a serious accident later that day, totaled her car and another--she and the passengers in the other car were hospitalized but luckily, no one died. They eventually sued Jiffy Lube, so well...it was a no-brainer. I had already been fired, though--day after the accident.
needless to say, I still feel horrible about it.