Not enough here to go on, except that the media is more than a little sparse on the details and they're more into the sensationalism than fact.
Mom was 27 or so when she had the kid, so theoretically grandma could be 49 or older. Wonder where the daddy was?
It could also be an overly rambunctious kid horsing around and an overzealous domestic violence policy coutesy of the local PD. Mom dials 911, says her nose is broken and that the kid hit her. All of a sudden the cops are there before the ambulance is looking for an arrest.