I've just investigated the contents of my Bushnell Trail Camera. I wasn't expecting much because the camera was pointing away from the front of the house. However, I found some fox activity that roughly matches the time of the shriek. The sequence starts at 11:56pm BST. There are two foxes in the frame. Fox 1 is crouched quite defensively. It is blurred as if it is moving. Fox 2, further up the slope is looking down at fox 1. The next shot, below is clearer.
|11:56pm - One second after the initial shot, fox 1 is now sitting.|
|One second later, it is obvious that the fox is eating something.|
|14 seconds later, fox 1 has temporarily left its meal to meet fox 2.|
|20 seconds after meeting fox 2, fox 1 has taken it's meal down the slope.|
So that's mother nature being ruthless. I don't know what was killed. I found it upsetting to find the bones but it didn't look like someone's pet or livestock. I'm not even sure if the fox was the killer. There are plenty of potential culprits that visit our garden and foxes do like to scavenge others' kills.