Although I don't agree that someone in distress should be left alone, I would feel I was invading this persons privacy in this situation if I took the photograph myself.

My own rule of thumb is, I wouldn't like my own privacy invaded in this situation.

Sometimes we have to see ourselves in the same situation before we can realise how much stress or trauma we are causing another person.

Photography is a wonderful art for recording experiences, as long as it causes no suffering to anyone else. After all, we wouldn't disturb a nesting bird for the art; would we?