Three sisters who escaped a home prison set up by their stepfather and mother in Arizona, were tortured with a constant barrage of loud music and monitored 24/7 by cameras installed in their bedrooms for up to two years.
Tucson Police chief Roberto Villasenor said the girls' ordeal came to an end earlier this week, as the two younger siblings - aged 12 and 13 - managed to escape to a neighbour's house after their stepfather, Fernando Richter, 34, tried to attack them with a knife.
Police searching the house found the third 17-year-old sister locked in a bedroom, and arrested Richter and his wife, Sophia Richter, 32.
"They were imprisoned in their bedrooms for at least the last several months and possibly up to two years," Tucson police said.
They were kept in filthy living conditions and allegedly only fed once a day.
The girls were held in separate rooms fitted with round-the-clock video security and an alarm system.
"Their movements were controlled - when, where and how they went to the bathroom, when they were fed," Villasenor said.
"[They] told patrol officers that they had not seen each other in almost two years," Tucson police captain Mike Gilooly added.
The police chief said music was played out loud throughout the day in the soundproof rooms.
In an apparently sadistic game, when the girls appeared to enjoy the music this was replaced by white or static noise.
"What the kids are telling us, it was 24-7 either loud music or static," Villasenor said.
Police said officers could not hear the music as they entered the premises as towels had been shovelled into duct works and under the room's doors.
The Richters have been charged with emotional and physical abuse and three counts of kidnapping. The stepfather has also been charged with one count of sexual abuse.
The girls have been placed under the care of social services.