Some dogs can get aggressive when someone gets to close to their food dish or toys. The parents should not have left the child alone with the dogs. I have a Jack Russell that I would not trust with an adult let alone a child.
Yes , believe me I know all about JR's. Ours has never been aggresive to humans or cats but he is definatley the Alpha Male when it comes to the other four dogs, two of wich weigh 10 times as much as he does.