Escalator incident

I saw a man fall down the escalator at Kings Cross tube today. Well technically I didn't. I was on the down-escalator and across at the up-escalator, I saw a handful of pistachio nuts go flying up in the air and heard a falling-over noise.
Which sounds funny now that I'm writing it but at the time it wasn't.
As I got to the bottom I went to see what had happened and the escalator was empty apart from the pistachios owner who was rolling over and over slowly, like laundry in a washing machine, powerless to stop the momentum as the escalator continued moving upwards. It was like a sick cartoon.
It wasn't until afterwards, I realised that I had just been standing and watching, a motionless rubber-necker.
A woman shouted for someone to go and help him and a man punched the stop button but the escalator didn't stop. Found out later that they slow down to a stop gradually.
Finally conscious of my gormless-gawping I went to punch the stop button again to make sure it got the message and to try and make up for the fact that I had just stood there.
The rescuer ran to the tumbling pistachio man to help him he was then joined by a member of the underground staff and policemen.
Pistachio man seemed to be OK or at least he was able to walk up the now still escalator with assistance.
I feel guilty that I didn't leap to his assistance immediately, and not entirely reconciling my guilt by remembering my poorly, strapped-up ankle would have limited what I could do.
It was a terrible thing to see but more terrible for pistachio man. He was just getting on with his journey, enjoying his pistachios and then his pistachios were spread all over the escalator.