Check your local/state regs.  
What folks say on here really doesn't matter.

"A friend of mine, deceased now, used to have a lot of problems with neighborhood cats. He would shoot them in the stomach with a low velocity, subsonic .22 that would not disturb the peace and that allowed the cats to go home and die."

Don't take THIS advice. I'm not against dispatching a varmint, but do it humanely.