However, as others have pointed out, it seems that the guy wasn't killing the cats humanely. Perhaps, he was getting off on the pain and suffering.
Also, it doesn't appear that he had any way of knowing whether his victims were feral cats, or someone’s beloved pet. According to my extensive research into serial killers (i.e. watching TV cop shows); serial killers are sociopaths, with no ability to empathize with their victims. Normal people understand that pet owners can have a strong emotional bond with their pets. Anyone capable of empathy can empathize with that emotional attachment, and wouldn't hurt a pet because they wouldn't want to hurt the owner emotionally.
Im glad your extensive research is watching tv cop shows. Who knows the reason for his behavior??
If it was obvious he had quickly and cleanly subdued them before skinning them then I'd be quite confident in my assertion that he was doing this purely out of hunger, but his apparent torture or sloppiness may also be inexperience.
At one time, I taught a wilderness survival course where students were given live rabbits and chickens to kill and eat. Even though the students were taught the best ways to cleanly dispatch the animals, those that were not familiar or comfortable with killing animals for food were quite sloppy about it, and you would have been hard pressed to distinguish what they were doing from "torture" although that was the furthest thing from their intent.
The Link Between Animal Abuse and Serial Killers
National District Attorneys Association —
CRUELTY TO ANIMALS BY CHILDREN, SERIAL KILLERS & OTHER VIOLENT CRIMINALS
(March 3, 2006) (pdf file)
http://www.hsus.org/web-files/PDF/animal_fighting/ndaa-animal-cruelty-killers-2-28-06-_2_.pdf