As a teenager in the 1960s in Rancho Cordova, Calif., Joseph James DeAngelo often biked or drove his Chevy Bel-Air around the neighborhoods looking for easy targets to burglarize.

One day, DeAngelo — who later became known as the Golden State Killer — and a friend spotted an open garage door. The two teens got off their bikes and walked to the home. As they made their way up the driveway, a large German Shepherd approached them barking.

“[DeAngelo] backed up, scared of the dog, and he fell down and hurt his wrist,” says Sacramento County District Attorney Thien Ho, author of the newly released book, The People vs. the Golden State Killer. “And he was so angry that he took out a Cherry Bomb M-80 firecracker, lit it up and threw it underneath the dog and the dog blew up and got caught on fire and died.”

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“He had a thing about German Shepherds,” Ho tells PEOPLE. “He abused German Shepherds in other situations. And so, the guy that he was with, the other teenager says, ‘Don’t hurt the dog. Don’t hurt the dog because it’s just doing its job. It’s protecting its home.’ But DeAngelo couldn’t help himself. He blew up the dog.”

Ho says DeAngelo grew up abusing animals, “which isn’t surprising for a serial killer.”

It turned out that DeAngelo’s dislike for dogs seemed to carry on throughout his life.

After he was arrested for multiple murders in 2018, a neighbor told authorities that the man — who was also known as the Visalia Ransacker, the East Bay Rapist and the Original Night Stalker — had threatened to kill their family dog.

“He remembered DeAngelo had threatened to kill their family dog for barking too loudly, leaving a message on their answering machine,” Ho wrote in the book. “’Shut that dog up, or I will bring a load of death to your home.’”

DeAngelo was caught via DNA testing and genetic genealogy. He was arrested on April 24, 2018 at his home in Citrus Heights.

In June 2020, the 72-year-old former police officer and mechanic pleaded guilty to 13 counts of first-degree murder and other crimes in order to avoid the death penalty. He was sentenced to life in prison without the possibility of parole two months later.

Today, he is housed in the Protective Housing Unit at a prison in central California.

“That’s where they put child molesters, rapists and snitches and gang dropouts,” says Ho. “He works in the mess hall in the cafeteria and he’s constantly looking over his shoulder, as far as I understand. He’s terrified of getting assaulted.”