Help needed sudden unexplained dead duck plus entire flock clearly distressed

[Magnolia Ducks]

I would hate to think that a neighbor would do such a thing, but if they did, its been my experience that if a duck has a broken neck it was pretty was to feel..

When my Blue egg duck got hit by a car, it was easy to tell her neck was broken. Just a glancing blow and the only damage was her neck broken.