Police arrested three people, including a 17-year-old girl, on suspicion of killing a couple and their friend inside a Southern California home over the weekend.

Fullerton police Sgt. Jon Radus would not say if the arrested teen was Katlynn Goodwill Yost, whom they had identified earlier as the missing daughter of two of the victims. He said she was located after authorities issued an alert, initially saying they were concerned about her safety.

Radus said state law prevents him from releasing the name of juveniles arrested for crimes.

"That said, a 17 year old female juvenile has also been detained in connection with the murders and is in the custody of the Orange County Juvenile Hall," he said.

The arrests on Sunday came a day after a child called 911 to report her parents had died.

Officers who went Saturday morning to the home in the southeastern Los Angeles suburb of Fullerton discovered two men and a woman dead with signs of trauma to their bodies. Two girls, age 6 and 9, were found unharmed inside the home.

Radus identified the victims — Christopher Yost and Jennifer Goodwill Yost — as the girls' parents and described the third victim, Arthur William Boucher, 28, as a family friend. The cause of their deaths was under investigation.

Suspects Josh Acosta, 21, of Fort Irwin and Frank Felix, 25, of Sun Valley, were arrested Sunday morning and booked into jail for investigation of murder.

Radus did not disclose a motive but said the killings were not random and that the victims knew their attackers.

"We hope the quick arrest of these individuals will bring comfort to the community and assist the friends and family of those affected by this unthinkable crime," he said.

At a candlelight vigil held outside the family's home Sunday evening, those who knew the Yosts said they were loving parents and friendly neighbors.

Donna Trice, a former neighbor, said Christopher Yost was an auto mechanic and his wife a stay-at-home mom and jewelry maker.

"There's nothing that can justify what happened and why the parents were taken away from the children," she said.

Neighbors said the family liked to decorate their front yard for Halloween and invited kids to stop for candy and play games.

Friends and relatives of Boucher said he occasionally slept at the house and worked as a hotel custodian.

"He was always standing up for women in his family, me included," his girlfriend Joyce Burchett said through tears. "I'm at a complete loss."