Have you ever witnessed a robbery?

It’s sad that I have to preface my question with this, but I do not mean high prices at the grocery store or gas pump – I’m talking about a couple bad guys brandishing weapons – a real robbery.
If you have, what were the circumstances? Did you stick around or hightail it out of there? Did you have the urge to intervene? What emotions did you feel? Were you traumatized by the event?