"but when you are getting overrun with them you have to take measures."
Understandable.
Where I live in MA the animal control officer shoots the cats he collects with a shotgun. I think he's a jerk for doing it this way, as he could bring them to a vet and have them euthanized peacefully. I'm sure the vet would give him some kind of deal, as he's the animal control officer, but no, he blows them to bits. I had a 9 week old kitten that he confiscated and blew to bits because the cat, which hadn't yet been vaccinated, had come in contact with a rabid bat (left its head on my doorstep).
Personally, I think the guy gains some pleasure killing them this way...
Oh and I forgot to mention, his brother did time in Walpole for child rape. Warped family, to say the least.
I would keep your cat on a leash!