Teen-Ager Arrested in Slaying at Pizza Parlor : Crime: The 17-year-old is the third suspect to be held in the Jan. 14 Porter Ranch holdup. The mother of the victim says she is ‘very relieved.’

A 17-year-old suspected of killing an assistant manager at a Porter Ranch pizzeria has been arrested in San Luis Obispo County, Los Angeles police said Sunday.

Dusty Tyrone Castillo, of Simi Valley, was being held at Sylmar Juvenile Hall on suspicion of killing John Michael Holden, 19, during a Jan. 14 holdup at the Ameci In & Out Pizza & Pasta restaurant, said Los Angeles Police Detective Paul Tippin.

Two other teen-age boys previously were arrested and charged with involvement in the slaying but said they are innocent. Both are scheduled to be tried as adults.

According to police, two teen-age robbers entered the restaurant at 11229 Tampa Ave. about 6:30 p.m. and demanded money from Holden, a part-time student at Moorpark College. Holden handed over $450, but a robber shot him once in the upper torso anyway.

Holden did not normally work at night but had volunteered to cover an evening shift for a friend. He died at Northridge Hospital Medical Center shortly after being shot.

Holden’s mother, Carol Holden, said Sunday she was “very relieved” at Castillo’s arrest.

“Thank God,” she said. “He’ll never do this to someone else. I have no doubt that if he’d been allowed to stay free, to get off to another area, he’d have done that again.”

Tippin told a Los Angeles news service early Sunday that Castillo was arrested Friday afternoon in San Luis Obispo County. Tippin could not be reached later in the day and an LAPD spokesman, Cmdr. David Gascon, said he had no other details of the arrest.

Carol Holden, who works as a civilian property clerk at the LAPD’s Van Nuys Division, said the story of her son’s killing was aired last week on “Prime Suspect,” a television show that recreates unsolved crimes. She said she was unaware if the broadcast aided in Castillo’s arrest.

After a $30,000 reward was posted in the case earlier this year, police arrested two other boys, ages 16 and 17. Police said the 17-year-old, Alexander Velasquez, accompanied Castillo into the restaurant.

Velasquez, of Canoga Park, faces murder and robbery charges. He is scheduled for trial as an adult along with the 16-year-old boy, who has not been publicly identified. The 16-year-old is suspected of driving the getaway car, police said.

Detectives released the name and a photograph of Castillo at an April news conference after receiving permission from a Juvenile Court judge. Castillo also is a suspect in seven other business robberies in the San Fernando Valley that occurred between November and January, and police described him as very dangerous.

Six days after Holden’s killing, Castillo allegedly entered a TJ Maxx clothing store in Canoga Park, fired a shot into the ceiling and then pointed his handgun at a clerk and demanded money.

John Holden was killed at a time when he was turning around a sometimes troubled life, relatives and friends said.

Severely dyslexic but possessing a talent for art, he began skipping school and smoking marijuana at age 14. When he couldn’t get his hands on liquor, he swigged alcohol-laced cough medications.

He eventually was arrested for breaking into five homes in upscale neighborhoods of the north Valley. He was committed to a private psychiatric hospital and later transferred to the Pacific Lodge Boys Home, a Woodland Hills treatment facility for young offenders, where he spent two years.

At 18, he was hired as a driver for the Ameci restaurant and so impressed his bosses that he was promoted to assistant manager despite his youth.

He began taking art and black-history classes at Moorpark College. He had a girlfriend and had purchased a foreign sports car, which his mother called “John’s trophy to himself for making it.”

After his death, Carol Holden learned that her son had been returning to Boys Lodge regularly to counsel other troubled boys.

She received a note from one boy who said that after he ran away from the lodge, John had met with him for several hours and convinced him to return. “He was the first person I knew who cared for me,” wrote the boy, who later graduated and landed a job.

Carol Holden described her son as “a guardian angel at large.” A scholarship has been set up in his name at the Boys Lodge.