The callers seem to know when the kids leave for school and when they are home alone, Kuykendall said. Messages warned the McKays that there would be a shooting at their daughter's school.
The harassment, they said, feels relentless. Kuykendall installed a new security system for the house. Soon after, she got a voice mail from Restricted saying that the callers knew her security code.
Once, McKay said, when she was slicing limes in her kitchen, a call came in from Restricted. The voice said it preferred lemons.
As soon as the Kuykendall family met with police, they say they received warnings not to talk to the cops. Then a voice mail arrived: a recording of the conversation they'd just had with the police.
"The level of fear went from, 'This is a pain,' to an uncontrolled fear and anxiety level," said McKay.
Kuykendall said her family switched phones and opened new accounts twice, but the calls keep coming. "If we go a day without a call, that's a good day," Kuykendall said.
The callers have likely violated several laws, law experts say, possibly including federal wiretapping statutes. But the case has local law enforcement stumped.
"We're almost dumbfounded. We've never seen anything like this," said Fircrest Police Chief John Cheesman, who said he has known the Kuykendalls for years.
Cheesman said he is working with the Tacoma police and the Pierce County Sheriff's Department and has also contacted officials at the department of Homeland Security. But police still are not close to finding the perpetrators.
Most of the harassment appears directed at Courtney Kuykendall, police said, adding that most, but not all, of the calls have been traced back to her phone.
Police are not calling the 16-year-old a suspect, though the unusual tale has raised some eyebrows. "It wouldn't be prudent not to look internally" at the family, said Ed Troyer, a Pierce County Sheriff's Department detective.
"At this point, we aren't saying it's someone inside the family, but it's someone that is close enough to them to know this much about them," Tryer said. "It seems like it's someone who is tied into the group, a family member, a friend or an enemy."
He added, "I hope it isn't coming from within the family because it would be a waste of everyone's time."
" Heather Kuykendall is adamant that her daughter is not involved and said the calls kept coming even when they took Courtney's phone away. She said Courtney was too upset to speak to ABC News.
"We know it's not her," Kuykendall said of Courtney. "And we can't think of anybody we've made mad or if we've made any enemies."
The calls appear to be just the latest incarnation of so-called cyber-bullying. According to an April 2007 survey of middle school kids by online safety group WiredSafety.org, the most prevalent threat children face through new technology is not the 40-year-old pedophile, but the kid sitting next to them in math class.
At least 85 percent of the middle schoolers polled said they have been cyber-bullied in the last year -- picked on by another child, often anonymously, through the Web or a cell phone.
"These situations recount how kids are hurting other kids -- taking the bullying off of the playground and into a much more anonymous, and often more painful encounter on the phone and online," said Parry Aftab, WiredSafety's director and a well-known Internet security and cyber-crime lawyer.