Of all the voices in the audio, the photographer's was probably the most level headed, and none of his questions were answered by the police, who did appear to be grasping at straws. Of course he didn't seem to be answering their questions (but did provide his ID when requested, a sign of cooperation), but he didn't have to unless the police provide the particular law under which they are entitled to the details.
I'm inclined to believe that the original police officer probably made an initial (small) mistake, and rather than admit it, and back down, had to keep going to avoid losing face, the illusion of authority and hope the accused capitulated. Not a strategy that should be heavily adopted by the police.
Is there any more to the story, i.e. a follow up on what happened after the audio went dead?
What is it with photographing children in public spaces? The law is quite clear: if you're in a public space you have no right to privacy, regardless of age. Or is there another law prohibiting photographing children entirely?