It's hard to believe . No attempt to call 911 or anything.
You never know how you are going to react until you are in a situation. Sometimes the right/obvious action isn't there in the moment everything goes down.
I was held up in Montreal with a few other people in an ATM bank lobby. I was younger and money was something very precious to me. I had my card in the ATM to make a withdrawal when this short French robber came in brandishing a small revolver. While people were handing him money/wallets, I pretended that I couldn't understand what he was saying. The other victims actually tried to help the robber explain that he wanted my money and access to the ATM, I nodded then pulled out my card and stepped aside from the machine at which point he was livid. He was calling me the most stupid bastard he had ever seen as I cocked my head in confusion. He was approaching me with the gun and idiot I was - if he got closer I thought I could get the gun. This would have been double dangerous because he had an accomplice standing by the entrance. I guess the time was ticking because he suddenly ran out.
I know in reflective thinking that what I did was stupid and dangerous. It was money that could be replaced. Obviously the robber was coming in for a quick score and we were not in danger of getting killed. We weren't until I reacted as I did. I could have got shot and if things escaladed, possibly the people around me.
The girl could have been in shock, looking down a shotgun does not trigger the Rambo like reflexes seen in the movies. It is so difficult to predict your reaction unless you have had training (eg. military/ LE) where your mind is making an rational appraisal of the threat and recognizing your options available.