The link is the story, posted almost three years ago now, of the day my sister was almost abducted in broad daylight on a busy street in Springfield, IL.
The short version is that she was being carried to a car by her abductor when a man came out of the gas station and saw what was going on. He ran over and punched the abductor, which made him drop my sister, who escaped. We never found out who he was, but it wasn't for lack of trying. I always wished I could have shaken that man's hand.
Yes, if I can get a good idea that the victim is not going to try to kill me, I will wade in. This incident taught me that all the legal quandaries are greatly simplified when a woman is actually being beaten, raped, or killed right in front of you.