I just don't think breaking someone's nose warrants a life threatening beating.
Also think there are a lot of ways a nose can get broken. If someone swings a punch unprovoked in someone's face then that's extremely scummy behaviour. If the police officer has had her nose broken whilst getting in between two other people fighting (which is entirely possible) then that changes things.
All we know for sure is that it's the police themselves who have the access to the most footage that can be used to get the truth out there. The longer they leave that, the worst they'll start to look.