Very sad but mustelids are voracious predators that are doing only what their instincts tell them to do.
I watched a
Stoat kill a
Rabbit yesterday-if it's any comfort, it was quick.
Sorry about your guineas, I have 2 myself, so would be very upset if the like happened to them. The only way to truly stop
Rabbits and guineas falling victim to preds are a VERY substantial hutch, very tough, small guage chicken wire or to have the hutch in a shed or conservatory. Runs from shops can be very weak and dug under by foxes so they need extra strengthening and an eye kept out for daytime opportunist predators.