It is my understanding that it’s pretty common for the police, when a suspect gets away with injuries, to ask the local hospital emergency departments to be on the lookout for people with matching injuries.
Why is it not a breach of medical confidentiality for the doctors/nurses to report these people to the police when they come in?
Well, it is a breach of medical confidentiality.
But I think you really mean “why is it not against the laws that require medical confidentiality”, and the answer to that is that those laws include exceptions for law enforcement.
I did a Google search for “HIPAA law enforcement exceptions” and a bunch of stuff came up. I’m sure the specifics are available if you want to go read through some long and dry legislation.