Most likely because he told the cop he was recording the whole thing.
But ... but ... robertpaulsen, it's not ethical. It's not faaaaaair.
You're the one crying about how it was unfair for this cop to be "set up".
I’m finding it really odd that the kid installed this camera and started the recording to set up the cop, and then told him he was being recorded. What kind of lame set up is that?