I've seen it as well. The "Vapor Lock" of people when action is required.
I was constantly yelled at by the WINO when we'd be driving along see an accident, and I'd be running toward the scene with first aid kit in hand. I could never understand her "I'm a nurse, but I'm a baby nurse, so I'm just going to sit in the car and not do anything." She would say that as a nurse she could be sued if she did anything "wrong". I printed and read to her Illinois "Good Samaritan" Law.
I've always been "Evaluate the scene as I run toward it type."
One place I worked at, I saw on of our temps get her sleeve caught in a conveyor and start to get drug toward the roller at the end. I ran and tackled her, ripping her sleeve but freeing her, and when I looked up from the floor the two other managers that I had been standing with where still where I had left them. They still had the "deer in the headlights" look on their faces for a moment or two until "time started back up again" and everyone started to run toward where the girl and I had piled up on the floor.