Both families should collaborate and work in tandem. Get the medical done. Collect all evidences such as CCTV footages etc.
File separate complaints for double pressure. If police refuses, post the application to write complaints via post office using registered post to the local police station. Get the receipt of such post.
Go to local commissioner office with another application that local police station is not writing our complaints, do attach registered postal receipt with it along with application Shared with local police station.
In commissioner application, mention that such application is cced to CMO as well.
Follow up.