Dana Point Youth Held in Slaying of San Clemente Girl : Arrest: The 16-year-old suspect lives in the complex where the shooting occurred and knew the victim, but investigators have not determined a motive.

Investigators have arrested a 16-year-old boy on suspicion of fatally shooting a San Clemente girl as she sat in her boyfriend’s car at a Dana Point apartment complex, but the motive behind the killing remains a mystery, authorities said Thursday.

Angela Lynn Wagner, 15, knew the suspect, but it was a “chance meeting” that resulted in the shooting Monday night, said Sheriff’s Lt. Dan Martini. “They just happened upon each other.”

The suspect, whose name was not released because of his age, lives in the apartment complex on Domingo Avenue in the Capistrano Beach section of Dana Point where the shooting occurred, Martini said. He was arrested without incident at a relative’s home in Anaheim late Wednesday and booked into Orange County Juvenile Hall on suspicion of murder.

On Thursday afternoon, neighbors at the complex stood in groups, somberly discussing the slaying of the popular sophomore at San Clemente High School.

The suspect’s mother stood inside the front door of her apartment, her face awash with tears, declining to comment.

Nearby, some teen-agers who know the suspect said that he isn’t a gang member and had no known reason for shooting Wagner, who was hit once in the chest with a bullet from a handgun.

One teen-ager said: “If he did something to that girl, I really feel it must have been an accident, knowing the person that he was.”

At nightfall, about 40 residents held a Rosary in the parking lot of the apartment complex in a ceremony presided over by Msgr. John Coffield of St. Felipe de Jesus Catholic Church, located just down the street. The residents held candles and offered prayers for Wagner and her family.

Perhaps compounding the grief was the senselessness of the girl’s death.

The victim’s boyfriend, 17-year-old Chris Antonio of Mission Viejo, has no idea why the suspect might have wanted to harm Wagner, Antonio’s sister, Toni, said Thursday.

Toni Antonio said her brother is hoping the whole thing was “an accident.” The Antonio family used to live at the apartment complex, where Chris Antonio and Wagner knew the suspect, although Wagner never lived at the complex.

According to Toni Antonio, her brother had been dating Wagner for the past seven months and they had known each other for two years.

“They were inseparable,” Toni Antonio said. “He felt like they were already married.”

She said her brother had planned to pick out a necklace this weekend to give Wagner for Christmas. Instead, he bought a white-gold necklace Wednesday for her funeral outfit.

Services for Wagner were set for today in Escondido.

The shooting occurred Monday about 6:45 p.m. while Wagner sat in her boyfriend’s 1980 Honda Civic in front of the apartment complex.

Chris Antonio had gone to an apartment in the complex to pick up an item from a family friend and was away from the car for just a short time, according to sheriff’s officials, who do not believe that Antonio and Wagner were involved with gangs.

When Antonio returned to his car, he found a dying Wagner having trouble breathing. She quickly lost consciousness and was later pronounced dead at Samaritan Medical Center-San Clemente, just down the hill from where she lived with her father and a younger brother.

She had been shot once in the chest at close range, said investigators, who initially gave Wagner’s age as 16 but corrected that Thursday to 15.

A series of clues leading to the arrest started coming together Wednesday, Martini said. “This doesn’t close the tragedy for the family, but it certainly puts an end to this part of the chapter,” he said.

Investigators believe the suspect acted alone in the shooting, but they have not determined a motive, Martini said. He declined to say whether investigators recovered the small handgun used in the shooting or to whom the weapon belongs.

Although investigators don’t know if the suspect is affiliated with a gang, they do not believe the shooting was related to gang activity, Martini said.

The district attorney’s office was expected to decide today what charges to formally press.

Meanwhile, the suspect was being held at Juvenile Hall pending a hearing to determine whether he remains in custody or is released to his parents.