Whilst they were away on holiday, one of our neighbours' dogs escaped from its pen in their garden, ran over to our garden and killed 2 chooks, and injured another and also our cockeral Monty. I was so distraught, as it seemed so different to losing them to a fox. Another neighbour managed to capture the dog so we were absolutely sure he was the culprit. Apparently, he was an old hunting dog.
When the neighbours returned from their break, they came round and offered to pay for the killed birds, though I actually also charged them for the injured one as I wasnt sure that she would lay again.
I was told later, that I should have reported it to the gendarmes and our Mayor as it would be noted and any more trouble with the dog would be very serious for the owners.
It took me a long time to get over the shock, so I know exactly how you feel. Big hugs coming from France.