I had a similar moment back at my old house...
I was taking the dog outside to do his thing and suddenly a elderly morning jogger walks by. My dog goes rushing towards the guy (because that's what he normally does, but with my Dad) I tried to lock the leash (the leash has a lock button) but then I lost the leash and my dog went bolting after the guy who went in the right side of the street to get away (he could've just stayed on the side walk and had a better chance) I grab onto the only thing I can, which was his leash strap while he's running. I eventually tugged him back and got a hold of his collar. As I finally got control of the dog, I shouted sorry to the old man who didn't pay attention to my holler. As he was still in shock. I got my dog inside instantly. I then explained the situation to my Dad and brother (my Mom was at work). Luckily I wasn't in any trouble, but had really blistered up hands from grabbing the leash strap. If I hadn't of done that though, my dog would be lost in the town (maybe eventually running into a car).
I will never forget that day, for it was a pretty tragic thing that happened.