The recent spate of cat killings isn't simple.
It is racially motivated.
Cats are the favorite pet/animals of Muslim/Malays. So this recent spate of cat killings may very well be a message being sent to the community of races who love these felines that they tend to let their cats roam around and shit everywhere.
At least that's what I found out from Malaysian Chinese. They hate cats because cats are favorite pets of Muslims and Muslims hate dogs which Malaysian Chinese love as pets. Some will cross the line to vent their anger at the decades of injustice on them by taking revenge on the Malay community's favorite animal, the cats.
Likewise in sg, it may be related too since the killing is no longer limited by just one person, as another copycat is on the loose too.