HELP! Guest is Threatening!

I BLOCKED all dates through the end of the year for our property, which is no longer available. However, on August 1st somehow a reservation was made for 15 & 16 August 2019. I immediately contacted the guest and stated that the property was not available and that the reservation should not have been able to be placed, as it was blocked. I asked him to cancel the booking and said that I would also contact Booking.com, which I did. 

Unfortunately he did not cancel and is now threatening to show up at our home and expects reimbursement even though Booking.com has the money, not me.

This reeks of a scam to me. I've been trying to contact Booking for assistance but cannot reach an actual person. 

This man is VERY threatening. I've told him that I would call the police if he comes to my property. What can I do??