I think people need to know more about their pets. Educating oneself on their body language, cues, how to train/communicate with as opposed to only treating like an anthropomorphic friend all the time I think maybe should be required to own a dog in certain parts of a city if no fence or anything is around the yard. I'm not big on making extra laws about stuff but preventative measures are where it's at. Can this ever happen again? Sure. Each parent and each person owning a particular animal should follow certain cautionary guidelines I think.
I had a friend when I was a kid. They had a German Shephard that was very nice whenever any of the family was around but would be snarling, baring it's teeth with rope taught whenever you tried to approach it when they weren't. Unfortunately, an extended family member ended up getting bit and they gave him away to a local shelter somewhere. Well trained sometimes isn't enough even when they had a fence up and took the necessary precautions after seeing a potential danger. However, it can't ever hurt to try and have a system to prevent some child wandering into the dog's territory or having a specific way of managing the dog.