My cat shot in the leg by a 22?

my cat lives on my parents 5 1/2 acre hills of TN.. is it Legal to shoot Cats in TN? and how do i tell if its a 22 cuz its no bb gun! im really upset, and we have experience in rescue, and everything so for this to happen to my cat....grrrr! he is more like a spoiled dog really, and grew up indoors, but i had to put him out at my mom because we are all allergic and i live in town. if aNYONE HAS INFO ON A ASPCA OR RESCUE IN TENN PLEASE LET ME KNOW!?