A horrible thing to happen.
I would get this friend of the guest evicted from your property @Amir47 as a trespasser. You will know laws in your country for doing this better than me.
This is nothing to do with Airbnb as it doesn't relate to a guest.
Do you have it in your house rules that only those who have booked and paid should be at the property. If so I would also look to get the booking cancelled for the guest as they bought someone into your home without permission.