Sunny, Starts with P is getting warm.
Visit the ATSB website, do a search on "Police".
The answers are there.
Accident Investigation is a federal function, as is Aviation regulation.
ATSB and the state police usually intertwine, despite any demarcation issues.
However, state police have over-riding powers in some circumstances, such as when death or injury result,
or there is a possibility that a crime may have been committed (the aircraft may have been used in regard to a crime).
The primary function of state police is normally to secure the site of an accident or incident,
to prevent interference to the scene pending the arrival of investigators, if appointed.
After all, they will usually be amongst the first public officials to arrive at the scene.
Sometimes the police will provide ATSB with details when ATSB are unable or cannot justify attendance.
Any questions initially asked by police will normally be in accordance with the ATSB handbook for police officer assistance,
and is normally to establish whether or not they have, or may have, some jurisdiction.
Usually, such as in your case, they can quickly determine the nature of the circumstances and ensure the right direction is taken.
Usually they will determine that they have no further interest.
Police of all states and the commonwealth have the power to detain or arrest, and do have the power to ask certain questions.
Likewise, you have a requirement to follow a lawful directive from a police officer, e.g. give your name and address, produce identification etc.
The state police will not and cannot institute proceedings against you for aviation offences, but can and may be a credible witness to such an offence.
So relax, answer the fairly simple questions if you can, and answer the mandatory ones as well.
If no one is hurt or killed, and you haven't committed a non aviation crime, that's normally the end of it.