BIG mistake. While I was looking there was a commotion at the door and I looked up to see the woman who runs the shop being pushed by an escaping shoplifter. Like an idiot I didn't let him run off... oh no, I had to be the hero so I grabbed at his arm. He promptly kicked me in the leg and pulled away. I staggered back and promptly fell over an old lady who was standing behind me, flattening her. By the time we'd sorted that out the thief was long gone, of course.
Result: A very shaken old lady whom I hope is okay. A bruised leg and two very badly bruised fingers, one of which may possibly be broken; I don't think it is, but I could be wrong. A half hour or so waiting for the police, and not much to show for it. If I hadn't tried to help he would have probably just run away.