another attack by pit bull

[FAHQTOO]

My poor ex mother-in-law. She lives out in the country, somewhat secluded a few miles out of town. She has a dog, 2 horses and a shit load of barn cats. She also watches my granddaughters during the week. They're always outside playing.
She called my boys out there on Wed fucking HYSTERICAL because 3 pit bulls showed up in her yard and annihilated 4 of her barn cats . Dead cats all over the front yard when they got there. She barely got the kids inside and they saw it all.
It happened again today. 3 more cats.
So now she's a prisoner inside her home because she's affraid to go outside. The cops won't do anything for whatever reason.
We know where they're coming from and the owners of the dogs don't seem to give a shit.
I think the dogs need to disappear quietly, but don't know to go about it.
I'm afraid if my son's shoot them, the people will hear it and start shit with their grandma. Her husband died last year and she has elderly neighbors across the road in their mid eighties. They're scared shitless too. I was thinking rat poison stuffed in some meat might take care of it. I have no fucking clue. The horses can't even leave the barn.
Any suggestions would be helpful.