How would most people step in to stop a robbery?

I guy robbed our store, he held the cashier and manager up with a hand gun and his friend was filming and collating the CCTV footage, we were realy busy and no one knew what was even happening, I saw him grab the manager and I just collasped and had a full on panic attack, I don't think any one would have done anything and even if they did I collasped so I could have been the only one, I feel terrible collasping over the sight of a gun is understandable but I still froze and now I feel terrible even though it turned out ok.