Something similar happened at teh animal shelter I helped at while in high school. I knew the murderer too & was friends with him, i thought he was a GOOD man... nope, he was a cat murderer... Instead of beating the cats to death, he put them to sleep, but in MASS numbers I remember all 3 rooms were FILLED with cats, including the semi outdoor pen. Then I come back the following weekend & there are only a handful of cats left & all were new (not including the working shelter cats that kept the mice at bay in the food room).

Due to the fact he wasn't breaking any laws nothing happened to him for a long time, so there were most likely hundreds of cats killed. However it was a no kill OSPCA shelter so after a lot of complaints by staff (he was the manager/owner person) the OSPCA arrived & cleared him out. I have no idea what happened after that, but I know he wasn't charged with anything as he didn't break any canadian laws