As RA-Aus don't have the powers to impose financial charges / fines / burden onto the Pilot (other than taking un-precedented court action), they will refer this to CASA to take action. Remember that the pilot has broken the CAO's & CAR's and not a specific RA-Aus rule, so he's under the full juristiction of CASA.
I'm all for "fun" in aircraft and may have seen some similar behaviours before or possibly been a little bit too close to the action
, however as these were complete strangers, I think he may have gone a little too far!