No YANBU at all. I was on a train into london once and it was stopped due to someone killing themselves on the line ahead. I was horrified by attitudes of my fellow travellers, every one of them complaining about being late.
Vengeful - I agree if you don't know the reason for the delay but it was announced on that occassion. We were all told that the train was stopped due to a death on the line. It's so sad that people are more worried about being a bit late rather than that someone has lost their loved one.
I agree with vengeful. The woman didn't know that someone had been killed. Roads are cordoned off all the time, lights could have been out, stolen car dumped by joyriders, dodgy vehicle clocking police and chucking something from window, burst water main, gas leak, there are a million reasons.
It is very sad about the old lady but I think you were BU to snap at someone who was having a general whinge and had no way of knowing what had actually happened.