Fear,misreading,situation,misread,bad,confusion

Yesterday, I was walking down the street when I saw an old man walking into a shop. His back seemed twisted out of shape and he was struggling to walk along.
Suddenly, a scallie (chav/ned/lower-class scummy-looking man) came out holding a tiny puppy by the scruff of fur on its back and the next thing you know, the old man's lying on the floor and falling over.
I couldn't tell for sure whether the scallie had shoved the puppy in the older man's face and/or tried to push him over or bumped into him, although I suspected it was the former at the time.

Anyway, I stared in the direction of the two men and the scallie made some kind of gesture at me that I couldn't see properly but didn't look nice.

My heart was pounding like mad and I was really scared that I was going to be attacked by him, but at the same time I didn't think it'd be a good idea to leave the scene. So I walked into the nearest phone box and tried pretending to be making a call (so I could see what was going on), but I couldn't see anything.

So I stepped out and I saw the scallie helping the older man up, but he couldn't do it himself. In the end, the scallie got about 4/5 other people to help him and everyone seemed to be worried about the older man.

_:_:_

Anyway, with that story being told, I hated myself for bot having done anything other than stare, but I couldn't read what was going on properly and I was afraid something bad might happen to me.
I've done that before when bad stuff has happened, and I hate myself for it. Is it normal/common?

Also, how can I learn to understand situations better so I don't end up doing it again?