I've come to the conclusion that I've never seen an actual pitbull in my entire life. In fact, I don't think they exist.
There is no breed standard according to earlier posts.
Jeez...
The dog that did this is a pitbull:
Here he is, next to his victim:
http://pic100.picturetrail.com/VOL639/2678265/21047685/396910225.jpg
The german shepherd actually isn't a proper german shepherd either. They are both randomly bred barrio dogs, intact males, poorly socialized, neglected and abused.
I show 100 people in my beat that second picture and ask "What breeds of dog?", all 100 will say german shepherd and pitbull. Nobody will guess "lab" or "chihuahua" or "poodle".
If people unanimously decide to call it a "cupcake", then that's what it is in plain speak. It's a pitbull.
Everyone knows a "white tank-top-style undershirt" is called a "wife beater". It's not correct, but that's what people call it.
The fact of the matter is that a certain style of canine was selectively bred and abused to make it violent. The low income people where I work, prefer these dogs, and propagate the problem. These people are illiterate, on welfare, perpetually drunk, and they won't differentiate a "Dogo Argentino" from a "pitbull", which apparently isn't even recognized by AKC.
Any dog, a couple generations removed from the neglect and abuse, and appropriately trained can be a fine dog, regardless of how it looks. I don't prejudge "pitbulls". I've rescued and rehomed pitbulls. I've grabbed a handful of courage and dragged a pitbull with a gunshot wound onto a blanket and lifted it's bloody dying carcass into my patrol car and transported it to the emergency vet.
My 14 year old mutt is a Chow/German-Shepherd mix. He's predisposed to breed prejudice. My next dog will probably be a Doberman or Rottie. I'll find one with an appropriate disposition and care for it and it will never be a problem.
Use your instincts when dealing with dogs.