Get a cage trap, bait it with sunflower seeds, and dunk the squirrels
in a large plastic bin of water. Dump the carcass in a plastic bag
and throw away, or you could just bury the dead squirrel for
fertilizer.

Squirrels hide and bury food all over the place, attracting rats and
mice. They also get into structures and chew on wires.

Don't believe the closet squirrel lovers who say that killing
squirrels does no good. That's a lie. The squirrel population is not
infinite. You can quickly reduce the squirrel population in your area
to zero in a short time. If later a squirrel moves it, trap it too.
Just leave the trap out and ready to go. Think about it: No sane
person would say not to trap moles, gophers, rats or mice on the
premise that there are "more out there somewhere". The funny thing is
that these same eco-nuts will object to fur trapping because it'll
cause extinction (among other things). They like to have it both
ways.