In a mountain-ringed development of tile-roofed homes in the Californian city of Perris, a nightmare was unfolding unnoticed – 13 siblings being held captive by their parents David and Louise Turpin, according to police

As Wednesday unfolded, investigators began their work of combing through the filthy, foul-smelling house looking for answers to the central question that has so far baffled authorities: why the Turpins apparently imprisoned their children before being arrested at the weekend, allegedly allowing them to starve and shackling them to furniture.

The tranquil suburban street where the Turpin home sits was clogged with news crews hoping to offer answers, as neighbours grappled with how the apparent imprisonment of siblings – aged two to 29 – could happen amid such normalcy.

A neighbour named Jose Mercado was trying to reconcile the horror – the Perris chief of police called it an act of “torture” – with his experience of a quiet community where the surrounding blocks bustle with hundreds of young trick-or-treaters during Halloween and residents proudly compete over the best Christmas lights display.

“We tend to look after each other here,” he said. “We help each other whenever we can – I think if someone had know anything they would have spoken out."

A light-up paper snowflake could be seen hanging in the window of the Turpin family home, where authorities said the family lived after previously residing in nearby Murrieta, California, and in Texas.

Turpin family: 13 siblings who were held captive by their parents Show all 15 1 /15 Turpin family: 13 siblings who were held captive by their parents Turpin family: 13 siblings who were held captive by their parents David and Louise Turpin with their 13 children who were being held captive by their parents in the family home in Perris, California. Facebook Turpin family: 13 siblings who were held captive by their parents Riverside County District Attorney Mike Hestrin speaks during a press conference announcing charges against David Turpin and Louise Turpin in relation to their 13 malnourished children found chained in their home, in Riverside. The two parents were charged with multiple counts of Child abuse, torture, abuse of dependent adults and false imprisonment and could face close to 100 years to life in prison if convicted. EPA Turpin family: 13 siblings who were held captive by their parents The home of David Allen and Louise Anna Turpin, where some of their children were bound with chains and padlocks. Reuters Turpin family: 13 siblings who were held captive by their parents David Allen Turpin poses for a mugshot after being arrested. Riverside County Sheriffs Department via Getty Turpin family: 13 siblings who were held captive by their parents One of the captives, a 17-year-old girl, escaped over the weekend and notified the Riverside Sheriff’s Department. Facebook/David-Louise Turpin Turpin family: 13 siblings who were held captive by their parents Perris residents watch as media gather in front of Turpin family home. The Sheriff's deparmtent said "the parents were unable to immediately provide a logical reason why their children were restrained in that manner." AFP/Getty Turpin family: 13 siblings who were held captive by their parents The children were found in dark and foul-smelling surroundings and "The victims appeared to be malnourished and very dirty,” the department said. Facebook/David-Louise Turpin Turpin family: 13 siblings who were held captive by their parents Neighbours stand outside the home. Getty Turpin family: 13 siblings who were held captive by their parents Louise Anna Turpin poses for a mugshot after being arrested. Not all of their victims were children: of the 13 victims, seven were between the age of 18 and 29, according to the Sheriff's Department. Riverside County Sheriffs Department via Getty Turpin family: 13 siblings who were held captive by their parents David and Louise Turpin in 2015. Authorities arrested them on torture and child endangerment charges, setting bail at $9m (£6.5m) apiece. Facebook/David-Louise Turpin Turpin family: 13 siblings who were held captive by their parents David Turpin and Louise Turpin appear in court for their arraignment in Riverside Reuters Turpin family: 13 siblings who were held captive by their parents David Allen Turpin and his wife, Louise Anna Turpin celebrate a renewal of their wedding vows with Elvis impersonator Kent Ripley in Las Vegas in 2011 A Elvis Chapel via AP Turpin family: 13 siblings who were held captive by their parents David Allen Turpin appears in court for his arraignment in Riverside. Prosecutors filed 12 counts of torture, seven counts of dependent adult abuse, six counts of child abuse and 12 counts of false imprisonment against Turpin and his wife, Louise Anna Turpin. The Press-Enterprise via AP Turpin family: 13 siblings who were held captive by their parents Neighbour Liza Tozier, and her son, Avery Sanchez, 6, drop off his large "Teddy" as a gift for the children. AP Turpin family: 13 siblings who were held captive by their parents Louise Turpin appears in court for her arraignment in Riverside. Authorities say the abuse left the children malnourished, undersized and with cognitive impairments. Reuters

“Comfort and joy,” proclaimed a sign on a house strung with coloured lights across the street from the Turpin home. Neighbours who were ferrying young children to school would not have met the Turpin children there. Authorities said they had been homeschooled, and the state’s education department records show Mr Turpin had received approval to run a private school – Sandcastle Day School – out of his residence.

In a statement, the California Department of Education (CDE) said: “We are sickened by this tragedy and relieved the children are now safe and authorities are investigating. Full-time private schools are required to register with the state to record their students’ exemption from compulsory attendance at public schools. Under California law, the CDE does not have the authority to monitor, inspect or oversee private schools.”

Three houses down from the Turpin residence, a neighbourhood watch sign announced that “We report all suspicious Persons & Activities to Our Law Enforcement Agency”. But nothing at the Turpin home signalled to residents something was amiss or compelled them to call the police – it was not until Sunday, when a 17-year-old daughter escaped from a window and contacted authorities, that help arrived. She and her siblings were so malnourished the adult children were initially believed to be minors.

Authorities are preparing to charge David and Louise Turpin, 57 and 49 respectively, with a number of counts of torture and child endangerment, having arrested them in the raid on Sunday. The pair – held on $9m bail – are set to appear in front of a Riverside County judge on Thursday.

Family members of the couple have also so far offered little insight into what occurred in the Turpin household and any motivation behind it, beyond snippets that suggest a regimented life.

“They weren’t allowed to watch TV. They weren’t allowed to have friends over – the normal things that kids do,” Teresa Robinette, a sister of Louise Turpin, told NBC’s Today show.

Ms Robinette said she had raised concerns about the children’s health, when she did speak to her sister, but they were played down by Mrs Turpin.

“I always made comments to Louise when I did talk to her, about, gosh, they are so skinny,” Ms Robinette said. “She would laugh it off and say David’s so tall and lanky, they are going to be like him.”

Another aunt, Elizabeth Jane Flores, said that she had tried for years to contact her sister, but to no avail. ”I want to reach out to the kids. I want them to know that for years we begged to Skype. We begged to see them, the whole family,” she said.

Ms Flores said that the family had always been private: “When that happens for 20 years, and it was before the kids even were there, you don’t think it’s abnormal.

“If it had been like two years ago that she cut us off, then we might think, wow, something’s not right... They were real private, and they didn’t come around much,” Ms Flores told ABC’s Good Morning America

Ms Robinette said that her family were “as hurt and shocked and angry and disappointed as everybody else” over the details released by the police, but she had a message for the 13 siblings.