An alternative viewpoint is that it was just a dogfight that the children happened to witness.
Jack Russells are known for being stupid and aggressive, frequently attacking much larger dogs. A likely scenario is that the kids were out for a walk with their stupid little rat dog which decided to attack the pit bulls, and the pit bulls fought back.
Notice that the kids were not hurt at all. If the pit bulls had really been going after them, they would have ignored stupid little rat dog and gone after the kids when they ran away. With the kids gone, little rat dog wasn't defending them, he was just acting like a Jack Russell.