agree with that weasel boxes with rat traps are the way to go.EDit: Make a weasel box and kill it , they're too fast to shoot. It will find a way to get in the run and kill the others if you don't do something soon.They're very small and can squeeze thru a 1 inch hole.So sorry for your loss! Wishing you the best in catching it!
https://www.hobbyfarms.com/build-diy-weasel-box-keep-hens-safe/
will how ever say i have shot 1 weasel, shotgun works well.