Sadly, because the dog is from an abusive background, and has killed a child, the police will likely rule that the dog be put down as he is considered a dangerous animal now.
However, it really goes back to the parents not taking responsibility. Among both sides - they will agree that the child should have never been left alone with the dog. You should never leave a young child alone with ANY pet, cat or dog.
Also, the reason many pit bulls are reported for biting is because of the fear that the dog is used for dogfighting and is aggressive. Also, many people who get bit and file a report will say it was 'a large black dog' or 'a large white dog with spots'. The officer filing the report will then suggest 'was it a pit bull?' then the victim will respond 'yes' automatically because it's the first breed to come to mind.
Other breeds don't get reported because they don't cause the damage a pit bull can (remember these dogs were bred specifically for bull fighting in Spain, they are able to take down a BULL), and the other breeds are not notorious for being used in dogfighting.
I have been around pit bulls - if bred and raised properly - they are a playful breed with a lot of energy. But they are extremely loyal to their owners and protective of their family, especially children.
Sadly, people who dog fight will breed specifically for aggressiveness and some of these make it into the mainstream where the unsuspecting owners have a badly bred American Pit Bull Terrier that has been bred for aggressiveness, but was 'culled' for not being aggressive enough as a pup. Or as in Polar's case, he came from an abusive situation. He reacts to only what he knows to protect himself. But I don't see this as an act of aggression. If it were, there would have been an incident within the first week of the child coming home from the hospital. I have a feeling the dog may have been trying to pick the child up by the 'scruff' and instead caused it's death. If the parents had been more careful such as NEVER putting the child on the floor with the dog around, and having a 'safe' area where the dog would be confined to during the child's playtime such as crating the dog or placing the dog into a confined kennel in the backyard while the family played outside or indoors. The dog would still get to be a part of the family, but they would have to understand that the child has more standing over the dog.
I feel bad for the family and I feel bad for the dog. Seriously, because of this event, the dog is unadoptable, will be declared 'vicious' and ordered to be put down. It's just a sad situation for everyone involved, including Polar.