I have been helping neighbors eliminate nuisance predators for years. The only member of the weasel family we have down here is mink. They hang along the waters edge so, they haven't been a problem for us, yet.
Because I often need good advice, I belong to several trapping forums. These guys tell me that trapping weasels is relatively easy. The weasel is a very small animal and can be caught with the typical old Victor RAT trap (not mouse trap).
Get on YouTube and watch videos on "trapping weasels". You may also watch videos on trapping fishers, martins and other members of the weasel family. What works for one will most likely work for the others.
When a weasel gets into a coop they usually kill every bird in it. Just like foxes will do!
Trapping foxes that frequent near humans is not as difficult as trapping them in the "wild". Around the house/chickens it is not crucial to conceal your scent as much. Again, watch some YouTube videos on trapping coyotes and on trapping foxes. The methods they will demonstrate are for catching them in mostly remote locations. Those same techniques will work exponentially better close to the house.
If these predators are killing near and on your property, it won't be long before they are killing your birds. Catch the killers and kill 'em.
