WARNING: Disturbing.

THE son of a US police captain has been sentenced to 16 years in jail for killing 21 cats and sexually abusing a dead one.

Robert Roy Farmer, 26, was sentenced on Friday in California, where a judge gave him double credit for 21 months already served. He will not have to register as a sex offender once released.

“It feels like another man committed these crimes, but I know it was me,” Farmer wrote in a letter that was read to the court by his lawyer. “I stole a member of their family. The fact that I was out of my mind was no excuse.”

Farmer, the son of a retired San Jose Police Department captain, was arrested on October 8, 2015 after a meth-fuelled killing spree.

He was found asleep in his car with a dead cat, chunks of fur, blood, fur-covered gloves, a hunting knife, and the collars of other cats, The Mercury News reported. The car was parked in a Home Depot parking lot.

The shocking saga began in September 2015 when cats began mysteriously disappearing from his area.

Neighbours shared disturbing stories of a man who had tried luring two cats into a backpack.

At the time, resident David Stine said one cat escaped and was later treated by a veterinarian for a “bite that was not an animal bite, as well as the bleeding head injury”.

Video footage from local resident Miriam Petrova’s security camera later showed a young man grabbing a 17-year-old orange tabby cat, GoGo, from a front veranda. Neighbours identified Farmer as the man in the video.

Farmer was charged with 21 charges of felony animal cruelty — one for each of his feline victims.

But the case took a shocking twist when an Animal Services necropsy report found signs of sexual abuse on the orange female tabby cat inside the car, including dilated genitalia.

Lab reports also matched Farmer’s DNA to DNA found under claw clippings.

“It’s still painful to come home knowing GoGo isn’t waiting for us,” Petrova said in a victim statement. “Now the only image burned in our minds is GoGo running for his life” on camera as Farmer chased after him.

“GoGo never hurt anybody,” she added, before addressing Farmer directly: “And for you, Robert Farmer — what have you done to GoGo? Where is he?”

Ms Petrova and other residents have set up a Justice for our CATZ Facebook page.